API 5CT N80 Casing Pipe

API 5CT N80 Casing is a medium-high strength Oil Country Tubular Good (OCTG) belonging to Group 2 of the API standards. Designed for deep wells and complex geological formations, it features a minimum yield strength of 80,000 psi (552 MPa), reaching up to 110,000 psi, and a minimum tensile strength of 100,000 psi (689 MPa).

The N80 grade is divided into two types: N80-1 and N80-Q. While their mechanical properties regarding tensile and yield strength are identical, the core difference lies in the heat treatment process: N80-1 is typically Normalized, whereas N80-Q must undergo Quenching and Tempering (Q&T). This specialized treatment provides N80-Q with superior low-temperature impact toughness and higher reliability in demanding environments.

In practical applications, N80 is commonly used in wells exceeding 3,000 meters, offering significantly higher resistance to collapse pressure and internal yield (burst) pressure than J55 or K55. Visually, N80-1 is identified by one red band, while N80-Q is marked with one red and one green band.

Need precise collapse and burst ratings for N80? Download the Full Technical Datasheet for your engineering files.

 

API 5CT N80 OCTG Pipe Color Band Identification

Used at the rig site for quick identification of the steel grade.

Grade	Color Band Identification
N80-1	One Red Band
N80-Q	One Red Band + One Green Band

 

API 5CT N80 Casing Pipe Chemical Composition

Grade	C	Si	Mn	P	S	Cr	Ni	Cu	Mo
N80 type 1 / Q	0.34-0.38	0.20-0.35	1.45-1.70	0.020	0.015	0.15	/	/	/

 

API 5CT N80 Casing Pipe Mechanical Properties

N80 is a medium-to-high strength steel grade. The "80" indicates a minimum yield strength of 80,000 psi.

Property	Imperial Unit (psi)	Metric Unit (MPa)
Yield Strength	80,000 - 110,000	552 - 758
Min. Tensile Strength	≥ 100,000	≥ 689
Min. Elongation	Calculated per API formula	Calculated per API formula
Hardness	Not specified by API	Not specified by API
Heat Treatment	Usually Normalized	Quenched & Tempered (Q&T)

 

API 5CT N80 oil well Casing Sizes 

Due to its higher strength, N80 is commonly used in deeper wellbore sections.

Outside Diameter (OD)	Nominal Weight	Wall Thickness	Inside Diameter (ID)	Drift Diameter
inch (mm)	lb/ft ( kg/m )	inch (mm)	inch (mm)	inch (mm)
5-1/2" (139.7)	17.00 (25.30)	0.304 (7.72)	4.892 (124.26)	4.767 (121.08)
	20.00 (29.76)	0.361 (9.17)	4.778 (121.36)	4.653 (118.19)
7" (177.8)	26.00 (38.69)	0.362 (9.19)	6.276 (159.41)	6.151 (156.24)
	29.00 (43.16)	0.408 (10.36)	6.184 (157.07)	6.059 (153.90)
9-5/8" (244.5)	40.00 (59.53)	0.395 (10.03)	8.835 (224.41)	8.679 (220.45)
	47.00 (69.94)	0.472 (11.99)	8.681 (220.50)	8.525 (216.54)

 

API 5CT N80 oilfield Casing Pipe Dimensional Tolerances

Standard tolerances for API 5CT N80 casing are as follows:

Item	Tolerance Requirement
Outside Diameter (D)	For D≥4−1/2": +1.00% / -0.50%
Wall Thickness (t)	-12.5%
Weight of Single Length	+6.5% / -3.5%
Straightness	Full length ≤ 0.2%; Pipe ends (1.5m) ≤ 3.2mm
Length Range	R1: 4.88-7.62m; R2: 7.62-10.36m; R3: 10.36-14.63m

 

API 5CT N80 oil well drilling pipe

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Inspection & Testing

To ensure the high-strength performance of N80, the following tests are required:

Hydrostatic Test: Mandatory for every length to verify integrity under high pressure.

Drift Test: Ensures no internal obstructions, following API standard dimensions.

Non-Destructive Testing (NDT): Typically Ultrasonic Testing (UT) or Electromagnetic Induction (EMI).

Charpy V-Notch Impact Test: Mandatory for N80-Q only.

Flattening Test: Conducted to verify the ductility and toughness of the material.

 

GNEE API 5CT N80 OCTG Casing Pipe process line

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GNEE API 5CT N80 Casing Pipe test equipments

 

GNEE API 5CT N80 Oil well casing pipe certificate

 

FAQ

Q1: What is the actual difference between N80-1 and N80-Q? Which one should I choose?
A: Their strength ratings are identical. The difference is the heat treatment: N80-1 is Normalized (lower cost, suitable for standard wells), while N80-Q is Quenched & Tempered (better toughness). If your project requires impact toughness or involves complex geology, N80-Q is the recommended choice.

 

Q2: Can N80 be used in sour environments containing Hydrogen Sulfide (H₂S)?
A: No. N80 is a standard steel grade and does not have anti-sour properties. It is susceptible to Sulfide Stress Cracking (SSC) in sour environments. For such conditions, please choose L80-1, C90, or T95.

 

Q3: Which thread connections do you provide?
A: We provide all API-standard threads, including Short Round Thread (STC), Long Round Thread (LTC), and Buttress Thread (BTC). Additionally, we offer processing for Premium Connections for high-sealing requirements.

 

Q4: How is N80 casing identified by color bands?
A: According to API 5CT, N80-1 is marked with one red band on the pipe body and coupling. N80-Q is identified by one red band and one green band. This prevents mixing different grades at the rig site.

 

Q5: What are your inspection standards?
A: We perform 100% of the inspections required by API 5CT, including Hydrostatic Testing, Drift Testing, Ultrasonic Testing (UT), or Magnetic Particle Inspection (MPI). All products are delivered with original Mill Test Reports (MTR).

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