Investigation of Fracture Mechanism of Casing-Drilling Steels

Abstract

The paper reports on an investigation of the fracture mechanism of both tensile and impact fracture in three types of casing-drilling steels. The results show that the tensile fracture surface of N80 steel includes fibrous zone, radiation area and shear lip zone, and those of both K55 and P110 steels include two zones; all the tensile fracture surfaces of three types of casing drilling steels show the ductile fracture mode, the ductile fracture mode indicated with dimples is observed on all zones; the impact fracture surface of the N80 steel possesses a combined quasi-cleavage and ductile fracture modes, a single fracture mode is observed on the fracture surface of both K55 and P110 steels, the K55 steel impact sample is fractured in a cleavage brittle manner, whereas the P110 steel impact sample is fractured in a dimpled ductile manner.