Determination of fracture toughness in the short transverse direction of low carbon steel pipes by compact-tension specimens completed by welded attachments

摘要

An experimental procedure for direct measurement of the fracture toughness values (K-IC) in the short transverse directions, of low carbon steel pipes, is proposed. The method consists of enlarging the material strip to be tested, by welding extensions so as to complete the dimensions of a valid compact tension specimen. Validation of the KIC results was done by the comparison between the values obtained from one-piece compact tension specimens and welded-completed specimens, both in the longitudinal direction (CL). Additionally, the effect of the steel microstructure orientation on the K-IC in the short transversal direction was studied. The results show that the K-IC values in the short transversal direction of low carbon steel pipes is as much as 20% lower than the CL direction. This is directly related to the relative orientation parameter (Omega(12)) and the banding degree (A(i)) of the pearlite bands in the microstructure, and the location of the crack plane with respect to the pearlite banding plane.