API 5CT is standard technical specifications for steel casing and tubing pipes used for oil wells in petroleum and natural gas industries.
Besides casing and tubing, it also includes pup joints, coupling stock, coupling material, and accessory materials, and establishes requirements for three product specification levels (PSL-1, PSL-2, and PSL-3). The requirements for PSL-1 are the basis of this standard.
Common Grades
• J55/K55
• N80/N80Q/L80
• C90
• R95/T95
• P110/C110
• Q125
Connections
API 5CT applies to the following connections which comply with API SPEC 5B:
• SC: Short round thread casing
• LC: Long round thread casing
• BC: Buttress thread casing
• NU: Non-upset tubing
• EU: External upset tubing
• IJ: Integral tubing connections
4 Groups of Grade
• Group 1: All casing and tubing in Grades H, J, K, N, and R
• Group 2: All casing and tubing in Grades C, L, M, and T
• Group 3: All casing and tubing in Grade P
• Group 4: All casing in Grade Q
General
- According to the API 5CT standard, steel material used for making the pipe billet shall undergo grain refining treatment. This steel shall contain one or more grain refining elements, such as a certain amount of aluminum, niobium, vanadium, or titanium, so that the austenite grains of the steel Grain refinement.
- Pipes supplied shall be manufactured in seamless type or EW type.
- Couplings, coupling stock, and coupling materials shall be seamless.
- Cold-drawn tubing pipe shall be properly heat treated; otherwise, it is not acceptable.
- Casing and tubing attachment materials shall be seamless pipes unless other types are stated on the order.
Heat Treatment
Heat treatment methods for API 5CT casing and tubing are a key factor to differ in each grade. Products requiring heat treatment shall be subjected to full-body and full-length heat treatment. The heat-treated upsetting product should be heat-treated in terms of its full body and full length after upsetting.
A separately heat-treated coupling blank is acceptable. If the finishing temperature is higher than the upper critical temperature of the treated steel and the pipe is air-cooled, it shall be normalized.
in the case of welding type, the weld seam shall be heat treated to a minimum temperature of 540 ℃(1000°F), or a certain treatment method shall be used to make the no untempered martensite structure in the weld.
N80 Type 1 and Type Q
Steel grade N80 type 1 products shall be normalized or normalized and tempered at the option of the manufacturer.
N80Q steel-grade products shall be quenched and tempered.
R95
R95 steel grade shall be quenched and tempered.
L80
When tempered at temperatures below 620 ℃(1150°F), grade L80 grade 13 Cr may be embrittled.
Straightening
R95
R95 casing and tubing shall not be stretched or expanded cold working after final tempering, except for cold working which is necessary for normal straightening and not more than 3% of compression cold working.
M65 and L80
Steel grade M65 and L80 products shall not be cold worked after final heat treatment except for the cold working required for normal straightening.
C90 and T95
C90 and T95 products can be cold-rotated straightened, but the pipe must be heated to a minimum temperature of 480 ℃(1000°F) degrees for stress relief after straightening. Light gag straightening for steel grade C90 and T95 products is allowed if necessary.
C110
If necessary, the product shall be cold-rotated straightened and subsequently stress-relieved at temperatures between 30℃to 55℃ (50°F to 100 °F) below the final specified tempering temperature, or hot-rotated straightened at temperatures not more than 165℃ (300°F) below the final specified tempering temperature. If necessary, it is allowed to do light gag straightening.
Q125
Gag-press straightening or hot-rotating straightening can be performed for straightening, but the temperature at the end of the rotary straightening should not be less than 400 ℃ (750°F) (unless a higher temperature minimum is specified on the order). If the hot rotary straightening method cannot be used, the product can also be cold-rotated straightened, but the stress relief must be performed at 510 ℃ (950°F) after straightening. The product cannot be subjected to stress relief after cold rotary straightening only by agreement between the purchaser and the manufacturer.
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