(1) The main importing countries of oil casings are: Germany, Japan, Romania, Czech Republic, Italy, Britain, Austria, Switzerland, the United States, and Argentina and Singapore. The import standards refer to the American Petroleum Institute standards API5A, 5AX, 5AC. The steel grades are H-40, J-55, N-80, P-110, C-75, C-95 and the like. 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 the like.
(2) The API has three lengths: R-1 is 4.88 to 7.62 m, R-2 is 7.62 to 10.36 m, and R-3 is 10.36 m to longer.
(3) Some imported goods are marked with the word LTC, that is, the filament buckle casing.
(4) In addition to adopting API standards, there are a small number of Japanese factory standards (such as Nippon Steel, Sumitomo, Kawasaki, etc.) imported from Japan. The steel grades are NC-55E, NC-80E, NC-L80. NC-80HE and so on.
(5) In the case of claim, there have been black buckles, thread damage, tube folding, broken buckles and thread tight distance tolerance, coupling J value is poor and other appearance defects and casing cracking, low yield strength, etc. quality problem.