N80 petroleum steel pipe is a kind of important equipment for oil drilling. Its main equipment also includes drill pipe, core pipe and casing, drill collar and steel pipe for small diameter drilling. The meaning of N80 is the grade of steel pipe divided according to the strength of the steel itself, and other steel grades such as J55, K55, N80, L80, C90, T95, P110, Q125, V150 and so on.

(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 4.88~7.62m, R-2 is 7.62~10.36m, and R-3 is 10.36m to longer.Some imported goods are marked with the word LTC, that is, the filament buckle casing.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.

(3) 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.

1.N80 Specifications and appearance quality

(1) The domestic casing is in accordance with SY/T6194-96, and the length of the casing is not fixed, and its range is 8-13m. However, casings not shorter than 6 m can be supplied, and the number must not exceed 20%.The inner and outer surfaces of the casing shall not have folds, hair lines, separation layers, cracks, rolling and crusting. These defects should be completely removed and the depth of removal should not exceed 12.5%.

(2) The outer surface of the coupling shall not have defects such as folding, hairline, separation, crack, rolling, crusting and so on. The surface of the casing and coupling threads shall be smooth and shall not be allowed to be burred, torn, and other defects sufficient to cause thread breakage to affect strength and tight joints.

2.N80 Chemical composition test

(1) According to SY/T6194-96. The casing and its couplings are of the same steel grade. The sulfur content is <0.045%, and the phosphorus content is <0.045%. Take chemical analysis samples according to the provisions of GB222-84. Chemical analysis was carried out in accordance with the relevant provisions of GB223.

(2) The first edition of the American Petroleum Institute ARISPEC5CT1988. Chemical analysis was prepared according to the latest version of ASTM E59 and chemical analysis was performed according to the latest version of ASTM E350.

3.N80 Physical property test

According to SY/T6194-96. For the flattening test (GB246-97) tensile test (GB228-87) and hydraulic test.According to the American Petroleum Institute APISPEC5CT 1988 first edition for hydrostatic pressure test, flattening test, sulfide stress corrosion cracking test, hardness test (ASTME18 or E10 latest version of the provisions), tensile test, lateral impact test ( ASTMA370, ASTME23 and the latest edition of the relevant standards are specified), grain size determination (the latest version of ASTM E112 or other methods).

4.N80 Packaging

According to SY/T6194-96, domestic casings should be bundled with steel wire or steel belt. The exposed portion of each bushing and coupling thread should be screwed with a guard ring to protect the threads.

5.N80 Other

According to the American Petroleum Institute standard APISPEC5CT 1988 first edition, casing steel grades H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P- 110, Q-125 a total of 10 kinds.

The bushings shall be supplied with threads and couplings or in the form of any of the following pipe ends:Flat end, round thread without coupling or with coupling, partial trapezoidal thread with or without coupling, straight-through thread, special end machining, sealing ring structure.