Introduction to  API specification 5CT seamless steel Pipe Oil Casing

API Specification 5CT Seamless Steel Pipe Oil Casing J55/K55/N80/L80/ C90/T95/P110/Q125/V150

the Oil and gas industry relies heavily on the use of seamless steel pipe oil casing for various applications. These casings are used to protect the wellbore during drilling and production operations. API Specification 5CT is a widely recognized standard for seamless steel pipe oil casings, and it provides guidelines for the manufacturing, testing, and inspection of these casings. Seamless steel pipe oil casings are made from high-quality carbon or alloy steel, and they are designed to withstand high pressure and temperature conditions. The J55, K55, N80, L80, C90, T95, p110, Q125, and V150 grades are commonly used in the industry, and each grade has its own specific properties and applications. J55 and K55 grades are typically used for shallow wells with low pressure and low temperature conditions. These grades have good toughness and are suitable for mild sour environments. N80 grade is a medium-strength casing that is commonly used in medium-depth wells. It has a higher tensile strength and better resistance to corrosion than J55 and K55 grades. L80 grade is a higher-strength casing that is used in deeper wells with higher pressure and temperature conditions. It has a controlled yield strength and excellent resistance to corrosion. C90 grade is similar to L80 grade but has a higher yield strength. It is commonly used in high-pressure wells.

Tensile and Hardness Requirements
Grade			Yield Strength MPa		Tensile Strength	Hardness a,c		Specified Wall thickness	Allowable Hardness Variation b
	Type	Total Elongation Under Load			min MPa	max
			min	max		HRC	HBW	mm	HRC
1	2	3	4	5	6	7	8	9	10
H40	—	0.5	276	552	414	—	—	—	—
J55	—	0.5	379	552	517	—	—	—	—
K55	—	0.5	379	552	655	—	—	—	—
N80	1	0.5	552	758	689	—	—	—	—
N80	Q	0.5	552	758	689	—	—	—	—
R95	—	0.5	655	758	724	—	—	—	—
L80 L80	1	0.5	552	655	655	23	241	—	—
L80	9Cr 13Cr	0.5	552	655	655	23	241	—	—
		0.5	552	655	655	23	241	—	—
C90	1	0.5	621	724	689	25.4	255	£12.70	3
								12.71 to 19.04	4
								19.05 to 25.39	5
								³ 25.40	6
T95	1	0.5	655	758	724	25.4	255	£12.70	3
								12.71 to 19.04	4
								19.05 to 25.39	5
								³ 25.40	6
C110	—	0.7	758	828	793	30	286	£12.70	3
								12.71 to 19.04	4
								19.05 to 25.39	5
								³ 25.40	6
P110	—	0.6	758	965	862	—	—	—	—
Q125	1	0.65	862	1034	931	b	—	£12.70	3
								12.71 to 19.04 19.05	4
									5
a In case of dispute, laboratory Rockwell C hardness testing shall be used as the referee method.
b No hardness limits are specified, but the maximum variation is restricted as a manufacturing control in accordance with 7.8 and 7.9.
c For through-wall hardness tests of Grades L80 (all types), C90, T95 and C110, the requirements stated in HRC scale are for maximum mean hardness number.

T95 grade is a higher-strength casing that is used in deep and high-pressure wells. It has a controlled yield strength and excellent resistance to corrosion and sulfide stress cracking. P110 grade is a higher-strength casing that is used in deep and high-pressure wells. It has a higher yield strength and better resistance to corrosion and sulfide stress cracking than T95 grade. Q125 grade is a higher-strength casing that is used in deep and high-pressure wells. It has a controlled yield strength and excellent resistance to corrosion and sulfide stress cracking. V150 grade is a higher-strength casing that is used in deep and high-pressure wells. It has a higher yield strength and better resistance to corrosion and sulfide stress cracking than Q125 grade. Glass BottleAPI Specification 5CT provides detailed requirements for the manufacturing, testing, and inspection of seamless steel pipe oil casings. It specifies the chemical composition, mechanical properties, and dimensional requirements of the cas