(1) The main oil casing pipe importing countries are: Germany, Japan, Romania, Czech Republic, Italy, United Kingdom, Austria, Switzerland, United States, Argentina, Singapore also have imports. The import standards mostly refer to the American Petroleum Institute standards API5A, 5AX, 5AC. Steel grades are H-40, J-55, N-80, P-110, C-75, C-95, etc. The specifications are mainly 139.77.72R-2, 177.89.19R-2, 244.58.94R-2, 244.510.03R-2, 244.511.05R-2 and so on.
(3) Some imported goods are marked with LTC, that is, long-thread buckle casing.
(4) In addition to adopting API standards, casings imported from Japan still implement a small number of Japanese factory standards (such as Nippon Steel, Sumitomo, Kawasaki, etc.). The steel numbers are NC-55E, NC-80E, NC-L80, NC-80HE and so on.
(5) In the claim case, there have been black buckles, thread buckle damage, tube folds, broken buckles and close tolerances of the thread, excessive J value of the coupling, and other defects such as brittle cracking and low yield strength quality problem.
