On July 17, 2025, our domestic customer sent us another inquiry for ASTM A335 Alloy Steel Pipe in grades P11 and P91. This time, the customer specifically requested that the pipes be marked with designated prefixes to facilitate quick identification of the material and specifications during installation and inspection. We will strictly adhere to standards and customer requirements during production and shipment, ensuring that each pipe bears clear and accurate prefix markings for easy traceability and use. Furthermore, we will provide a Material Certificate (MTC) and quality inspection report based on the specific needs of the customer’s project, ensuring our products fully comply with international standards and the customer’s engineering application requirements.

Product List

ITEM	DESCRIPTION	MARKING	QUANYITY	UNIT
1	SMLS PIPE  A335 P11 STD 12″	E-STEEL SMLS PIPE A335 P11 STD 12″ L=6M HEAT NO.*** LOT NO. ***	6	M
2	SMLS PIPE A335 P11 STD 16″	E-STEEL SMLS PIPE A335 P11 STD 16″ L=6M HEAT NO.*** LOT NO. ***	6	M
3	SMLS PIPE A335 P91 STD 16″	E-STEEL SMLS PIPE A335 P91 STD 16″ L=6M HEAT NO.*** LOT NO. ***	6	M

Inspection of Alloy Steel Pipes

Outer Diameter and Wall Thickness: Measurements are taken using a Vernier caliper or micrometer, typically at multiple points across different cross-sections of the tube to ensure accuracy. Some modern production lines utilize automated inspection equipment for continuous measurement.

Length: Measurements are taken using a steel tape measure to ensure the tube length meets order specifications.

End Faces: Inspect the beveled edges and cuts at both ends of the tube to ensure they are flat, smooth, and free of burrs.

Spectral Analysis: Spectral analysis is a non-destructive testing method used to determine the chemical composition of alloy steel tubes. By analyzing the content of specific elements in the steel, it can be confirmed whether it meets the grade standards.

Wooden box packaging: Wooden box packaging is primarily used to protect alloy steel tubes during long-distance transportation, especially during sea transport. For tubes with special surface treatments or precision components, the interior of the wooden box is filled with cushioning materials such as foam or bubble wrap to prevent the tubes from colliding with each other.

ASTM A335 Alloy Steel Pipe Specification

Processing Method:	Seamless and Welded
Size Range	1/8” – 48” / DN6 – 1200
Thickness Schedule	SCH 20- SCH 160, XXS
Length	6m or 12 m or Random
Standard	ASME B36.10
Surface Treatment	Blasting and Painting, Epoxy Powder FBE, 2PE, 3PE Coating
Material Grade	ASTM A335 P11 / P12 / P 5 / P9 / P91 / P92, A213 T11 / T12 / T22 / T5 / T9 / T91 / T92. 15CrMoG, 12Cr1MoVG, 12Cr5Mo, 1Cr5Mo, Cr9Mo, 10CrMo910, 12CrMo4-5

ASTM A335 Alloy Steel Pipe Chemical Composition

Grade		P-5	P-9	P-11	P-12	P-22	P-91	P-91 shall also include the following:
Element	UNS Designation	K41545	S50400	K11597	K11562	K21590	K91560
Carbon		0.15 max	0.15 max	0.05 – 0.15	0.05 – 0.15	0.05 – 0.15	0.08 – 0.12	V at 0.18 – 0.25
Manganese		0.30 – 0.60	0.30 – 0.60	0.30 – 0.60	0.30 – 0.61	0.30 – 0.60	0.30 – 0.60	N at 0.030 – 0.070
Phosphorous, max		0.025	0.025	0.025	0.025	0.025	0.02	Ni at 0.40 max
Sulfur, max		0.025	0.025	0.025	0.025	0.025	0.01	Al at 0.02 max
Silicon		0.50 max	0.25 – 1.00	0.50 – 1.00	0.50 max	0.50 max	0.20 -0.50	Cb at 0.06 – 0.10
Chromium		4.00 – 6.00	8.00 – 10.00	1.00 – 1.50	0.80-1.25	1.90 – 2.60	8.00 – 9.50	Ti at 0.01 max
Molybdenum		0.45 -0.65	0.90 – 1.10	0.44 – 0.65	0.44-0.65	0.87 – 1.13	0.85 – 1.05	Zr at 0.01 max

Tensile Requirements of Alloy Steel Pipes 

Seamless
	P-5	P-9	P-11	P-12	P-22	P-91
Tensile Strength, min., psi
ksi	60	60	60	60	60	85
MPa	415	415	415	415	415	585
Yield Strength, min., psi
ksi	30	30	30	32	30	60
MPa	205	205	205	220	205	415

	P-91
Tensile Strength, min., psi
ksi	85
MPa	585
Yield Strength, min., psi
ksi	60
MPa	415

ASTM A335 Standard Ordering Information

Orders for material under this specification should include the following, as required, to describe the desired material adequately:

1. Quantity (feet, metres, or number of lengths),

2. Name of material (seamless alloy steel pipe),

3. Grade (Table 1),

4. Manufacture (hot-finished or cold-drawn),

5. Size using one of the following

6. NPS and schedule number

7. Outside diameter and nominal wall thickness

8. Outside diameter and minimum wall thickness

9. Inside diameter and nominal wall thickness, and

10. Inside diameter and minimum wall thickness.

11. Length (specific or random),

12. End finish (Ends Section of Specification A999/ A999M),

Alloy Steel Pipe Dimension

Nominal  Size		OD	Nominal Wall Thickness T
DN	NPS	OD	Sch10	Sch20	Sch30	STD	Sch40	Sch60	XS	Sch80	Sch100	Sch120	Sch140	Sch160	XXS
6	1/8	10.3	1.24		1.45	1.73	1.73		2.41	2.41
8	1/4	13.7	1.65		1.85	2024	2024		3.02	3.02
10	3/8	17.1	1.65		1.85	2.31	2.31		3.20	3.20
15	1/2	21.3	2.11		2.41	2.77	2.77		3.73	3.73				4.78	7.47
20	3/4	26.7	2.11		2.41	2.87	2.87		3.91	3.91				5.56	7.82
25	1	33.4	2.77		2.90	3.38	3.38		4.55	4.55				6.35	9.09
32	1 1/4	42.2	2.77		2.97	3.56	3.56		4.85	4.85				6.35	9.7
40	1 1/2	48.3	2.77		3.18	3.68	3.68		5.08	5.08				7.14	1015
50	2	60.3	2.77		3.18	3.91	3.91		5.54	5054				8.74	11.07
65	2 1/2	73.0	3.05		4.78	5.16	5.16		7.01	7.01				9.53	14.02
80	3	88.9	3.05		4.78	5.49	5.49		7.62	7.62				11.13	15.24
90	3 1/2	101.6	3.05		4.78	5.74	5.74		8.08	8.08
100	4	114.3	3.05		4.78	6.02	6.02		8.56	8.56		11.13		13.49	17.12
125	5	141.3	3.40			6.55	6.55		9.53	9.53		12.70		15.88	19.05
150	6	168.3	3.40			7.11	7.11		10.97	10.97		14.27		18.26	21.95
200	8	219.1	3.76	6.35	7.04	8.18	8.18	10.31	12.70	12.70	15.09	18.26	20.62	23.01	22.23
250	10	273.0	4.19	6.35	7.80	9.27	9.27	12.70	12.70	15.09	18.26	21.44	25.40	28.58	25.40
300	12	323.8	4.57	6.35	8.38	9.53	10.31	14.27	12.70	17.48	21.44	25.40	28.58	33.32	25.40
350	14	355.6	6.35	7.92	9.53	9.53	11.13	15.09	12.70	19.05	23.83	27.79	31.75	35.71
400	16	406.4	6.35	7.92	9.53	9.53	12.70	16.66	12.70	21.44	26.19	30.56	36.53	40.49

What is ASTM A335 Material?

ASTM A335 is a standard for seamless alloy steel pipes established by the American Society for Testing and Materials (ASTM), primarily used in pipeline systems operating under high-temperature and high-pressure conditions. This standard covers various grades of chromium-molybdenum alloy steel, such as P1, P5, P9, P11, P22, P91, etc., which exhibit excellent high-temperature strength, creep resistance, and corrosion resistance. They are widely applied in fields such as power plant boilers, petrochemical plants, refining facilities, and heat exchangers.

Advantages of Alloy Steel Pipes

High Strength and Toughness: Alloying elements significantly increase the yield strength and tensile strength of steel pipes, enabling them to withstand higher pressures and loads. At the same time, they maintain good toughness, making them less susceptible to brittle fracture.

Excellent High and Low-Temperature Resistance: Alloying elements enhance the pipe’s long-lasting strength and oxidation resistance at high temperatures, ensuring it retains excellent mechanical properties even at extremely low temperatures.

Excellent Corrosion Resistance: The addition of elements such as chromium and nickel significantly enhances the corrosion resistance of alloy steel pipes.

Wear Resistance: Some alloy steel pipes exhibit excellent wear resistance, effectively resisting erosion and wear caused by flowing media, extending their service life.

Applications of Alloy Steel Pipes

Oil and Gas Industry

Power Industry

Chemical and Pharmaceutical Industry

Aerospace and Automotive Industry