API 5L in the casing and tubing grade; in API 5Lin the casing and tubing is divided into four groups, 19 grade. According to manufacturing methods, seamless and welded pipe is divided into two categories. In addition to L80-9Cr, L80-13Cr, C90-1, C90-2, T95-1, T95-2 limit the use of a total of six grades of seamless pipe, the other can be used in addition to seamless steel grade can also use resistance or Induction welding production Longitudinal. The heat treatment process, in addition to 1 set of 3 steel grade, the first group N80Q class, 2,3,4 in the group of the API 5L casing and tubing is divided into four groups, 19 grade. According to manufacturing methods, seamless and welded pipe is divided into 14 grades of steel must be full-length quenching and tempering treatment, and the second group of eight grade specifies the minimum tempering temperature. For Group 1, Group 2 and 3 of M65 grade group of seven grade provides only S, P content maximum, rather than requiring other major chemical composition. For Group 2 and Group 4 of 12 grade provides the chemical composition requirements.
OCTG tubing and casing in the API standard threaded connection consists of two parts: the pipe or coupling, or the public side and mother side. With external thread is called pipe or public side. Called a female or female coupling end. Two male end of a coupling link, coupling is a slightly larger diameter than the pipe short pipe. Both ends of the car within the thread. All API threaded and coupling with the casing and line pipe is not thick. Outside the tubing is not thick or thicker. The diameter of the pipe end is approximately equal to the diameter of the tube. However, thicker diameter than the tube side of the big. Tubing connected the two ends of the whole is thickened. API specification includes four threads, thread the line pipe, round thread, buttress thread, and direct-type thread. Line pipe, round thread, buttress thread in the screw together with the access requirements of assembly, to fill the grease in sealed together to prevent leakage from the thread. Straight bushing threaded end designed to seal. Extreme-connected metal to metal seal is sealed to achieve. The main parameters of API standard thread API standard thread of the main parameters are: thread length (in addition to buttress thread): thread starting from the (tube side) to the vanishing point of the length. Thread height: the screw tip to the distance between the bottom teeth. Pitch: that thread at any point along the axis to the adjacent teeth of the corresponding point distance. Threaded taper: that is expressed in inches per inch diameter screw thread length changes. Close distance: the pipe or coupling end to a ring or plug gauge tightened position along the axis between the measured distance.
Standards in API 5L, casing and tubing grade indicating its yield strength and some special features. Grade marked with a letter and usually two or three digits, such as the N80. In most cases, according to the order of letters in the alphabet, the more the subsequent letters that represent the greater the yield strength of the tube. For example, N80 a yield strength of steel than the J55 big. Number sign is one thousand pounds per square inch, said the pipe to determine the minimum yield strength. For example: N80 grade minimum yield strength of 80,000 lb/in2. API SPEC 5CT Standard grade are listed in the casing: H40, J55, K55, N80, M65, L80, C90, C95, T59, P110, Q125; casing grade are: H40, J55, N80, L80, C90 , T59, P110. 188.8.131.52 To meet the special geological conditions the environment field, at home and abroad to use non-API tubing and casing types.
In addition to API standard casing, but also research and development of domestic oil to meet the special geological conditions of the environment to use non-API casing, including: ultra-high intensity for deep well tubing, casing; high resistance to collapsing casing; oil and gas wells using hydrogen sulfide hydrogen sulfide stress corrosion resistance tubing, casing; for low-temperature high-strength oil and gas wells tubing, casing; for only carbon dioxide and chloride ions, almost no hydrogen sulfide corrosion environment, the use of tubing casing; for hydrogen sulfide, carbon dioxide and chloride ions of the three co-exist with a strong corrosive environment of tubing, casing.