Failure analysis of ∅127mm IEU G105 drill pipe wash out

One ∅127 mm IEU G105 drill pipe body washed out infrequently just after 126 h of pure drilling time. This paper gives a systematic analysis in consideration of material quality and loading condition on drill strings. Measurement and inspection were performed on configuration, chemical composition, mechanical performance, metallography and micro-fractography. It’s thought that the drill pipe washed out accident was premature fatigue failure accident. Failure reason is the 0.35 mm decarburization layer caused by improper heat treatment and mechanical damage because of improper operating on the out surface. Under the effect of fluctuating stress, cracks originated from decarburization layer and grew rapidly. When cracks propagated through the wall thickness, drill pipe washed out.

► Drill pipe’s material and fracture character was tested and analyzed.
► The 0.35 mm decarburization layer was found in pipe’s out surface.
► Failure is fatigue failure and fatigue cracks originated from decarburization layer.