ASTM A335 P91 Pipe is a high-performance seamless ferritic alloy steel pipe developed for elevated temperature and pressure environments. Also referred to as 9Cr-1Mo-V pipe, P91 is designed to provide enhanced creep strength, thermal fatigue resistance, and oxidation protection in critical piping systems.

The alloy composition of P91 includes approximately 8.0–9.5% chromium, 0.85–1.05% molybdenum, and small additions of vanadium (0.18–0.25%) and niobium (0.06–0.10%), delivering superior structural stability at temperatures up to 650°C. This makes it ideal for use in superheaters, reheaters, heat exchangers, and power plant steam lines.

Manufactured through seamless hot-finished or cold-drawn processes, ASTM A335 P91 alloy pipe ensures excellent dimensional accuracy, weldability, and long-term operational reliability. It requires specific heat treatment (normalizing at 1040°C and tempering at 760°C) to achieve desired mechanical properties and prevent embrittlement.

Available in sizes ranging from 1/2” to 24” (DN15–DN600) with wall thicknesses up to SCH 160 or customized, P91 pipes are typically supplied with beveled or plain ends. Optional surface coatings such as black paint, varnish, 3LPE, or FBE enhance corrosion resistance and support extended service life.

ASTM A335 P91 is widely used in ultra-supercritical (USC) boiler systems, high-efficiency power generation facilities, and petrochemical plants where prolonged exposure to thermal and mechanical stress demands the highest material integrity.

ASTM A213 / A335 T91 / P91 Pipe Stock List

Detailed specifications including outer diameter, wall thickness, quantity, weight, and length.

Spec	Grade	O.D. (mm)	W.T. (mm)	Pcs	Weight (T)	Length (m)
SA213 /A335	T91 / P91	16.00	3.00	360	3.10	6-11.5
SA213 /A335	T91 / P91	18.00	4.00	214	2.38	5-7
SA213 /A335	T91 / P91	22.00	7.00	171	3.57	7-9
SA213 /A335	T91 / P91	25.00	7.00	179	4.48	6-8
SA213 /A335	T91 / P91	28.00	3.50	168	2.86	5-6.5
SA213 /A335	T91 / P91	28.00	4.00	142	2.71	5-6.5
SA213 /A335	T91 / P91	28.00	5.00	105	2.40	5-6.5
SA213 /A335	T91 / P91	32.00	6.00	231	7.16	5-6.5
SA213 /A335	T91 / P91	32.00	7.00	232	8.06	5-7
SA213 /A335	T91 / P91	32.00	8.00	162	6.18	8.02-10.71
SA213 /A335	T91 / P91	34.00	6.50	146	5.18	5.5-5.9
SA213 /A335	T91 / P91	33.00	9.00	152	6.52	9.08-11.42
SA213 /A335	T91 / P91	34.00	12.00	96	5.03	6.4
SA213 /A335	T91 / P91	38.00	4.00	84	2.27	7-9
SA213 /A335	T91 / P91	38.00	5.00	141	4.62	9.58-11.62
SA213 /A335	T91 / P91	38.00	5.50	108	3.83	7-8
SA213 /A335	T91 / P91	38.00	6.00	144	5.49	7-8
SA213 /A335	T91 / P91	38.00	8.00	243	4.86	7-8
SA213 /A335	T91 / P91	38.00	9.14	141	7.21	12
SA213 /A335	T91 / P91	38.00	10.00	162	8.82	8-10
SA213 /A335	T91 / P91	41.30	4.00	82	2.41	8
SA213 /A335	T91 / P91	41.30	7.00	98	4.63	12.05
SA213 /A335	T91 / P91	41.30	11.00	131	8.59	6-11.5
SA213 /A335	T91 / P91	48.00	4.00	18	1.69	6-10
SA213 /A335	T91 / P91	51.00	4.00	20	1.26	12
SA213 /A335	T91 / P91	51.00	7.50	36	2.33	9
SA213 /A335	T91 / P91	51.00	8.00	38	2.73	7-10
SA213 /A335	T91 / P91	51.00	12.00	62	5.76	4.37
SA213 /A335	T91 / P91	51.00	13.00	35	3.34	8
SA213 /A335	T91 / P91	51.00	14.00	10	0.86	5.8-7.2
SA213 /A335	T91 / P91	54.00	4.00	114	4.53	10
SA213 /A335	T91 / P91	54.00	8.50	82	6.30	11
SA213 /A335	T91 / P91	54.00	9.00	51	4.10	3.8-7
SA213 /A335	T91 / P91	54.00	10.00	29	2.53	12
SA213 /A335	T91 / P91	54.00	13.00	36	3.81	8.5-9.21
SA213 /A335	T91 / P91	57.00	9.00	29	2.49	10-11.4
SA213 /A335	T91 / P91	57.00	10.00	46	4.30	6-10
SA213 /A335	T91 / P91	57.00	13.00	110	12.50	8
SA213 /A335	T91 / P91	57.00	14.00	56	7.65	4.2-5.64
SA213 /A335	T91 / P91	57.00	15.00	91	11.39	9
SA213 /A335	T91 / P91	60.30	8.74	1	0.26	6.01
SA213 /A335	T91 / P91	60.00	9.00	55	4.05	8
SA213 /A335	T91 / P91	60.00	10.50	62	6.16	7
SA213 /A335	T91 / P91	60.00	12.00	53	3.97	6-8
SA213 /A335	T91 / P91	42.00	3.50	93	2.57	11
SA213 /A335	T91 / P91	42.00	4.50	151	5.06	8-9
SA213 /A335	T91 / P91	42.00	5.00	173	7.10	8-12
SA213 /A335	T91 / P91	42.00	6.00	83	2.60	8-9
SA213 /A335	T91 / P91	44.50	5.00	59	2.29	8-9
SA213 /A335	T91 / P91	45.00	7.00	68	3.59	12
SA213 /A335	T91 / P91	44.50	7.50	51	2.77	7-9
SA213 /A335	T91 / P91	44.50	8.00	45	3.08	8-11
SA213 /A335	T91 / P91	44.50	10.00	63	4.25	9-
SA213 /A335	T91 / P91	44.50	11.00	86	6.20	7-9
SA213 /A335	T91 / P91	45.00	4.00	29	0.98	7-9
SA213 /A335	T91 / P91	45.00	7.00	31	2.35	12
SA213 /A335	T91 / P91	45.00	8.00	72	4.29	10- 12
SA213 /A335	T91 / P91	45.00	9.00	81	5.21	11.71-12
SA213 /A335	T91 / P91	45.00	10.00	118	7.65	8-12
SA213 /A335	T91 / P91	45.00	12.00	83	6.53	9.5
SA213 /A335	T91 / P91	45.00	13.00	76	6.28	8.03-8.41
SA213 /A335	T91 / P91	48.00	6.50	52	2.84	7-9
SA213 /A335	T91 / P91	48.00	7.14	82	4.67	8-12
SA213 /A335	T91 / P91	48.00	7.50	124	7.48	7-12.03
SA213 /A335	T91 / P91	48.00	9.00	56	3.81	11-12
SA213 /A335	T91 / P91	48.00	10.00	49	3.68	7-9
SA213 /A335	T91 / P91	48.00	11.50	16	1.60	10-11
SA213 /A335	T91 / P91	63.00	4.00	18	0.73	6-8
SA213 /A335	T91 / P91	63.00	5.00	13	0.65	6-8
SA213 /A335	T91 / P91	66.00	5.00	29	1.76	10-12
SA213 /A335	T91 / P91	70.00	8.00	72	8.81	8
SA213 /A335	T91 / P91	70.00	16.00	1	0.12	8.47
SA213 /A335	T91 / P91	76.00	4.50	1	0.09	8
SA213 /A335	T91 / P91	76.00	6.00	2	0.10	8.47
SA213 /A335	T91 / P91	76.00	18.00	29	4.12	6-6.8
SA213 /A335	T91 / P91	89.00	6.50	37	3.94	5.26-5.86
SA213 /A335	T91 / P91	89.00	20.00	12	3.29	6
SA213 /A335	T91 / P91	102.00	7.50	32	4.51	6.95
SA213 /A335	T91 / P91	108.00	12.70	22	5.03	6.65
SA213 /A335	T91 / P91	114.30	22.00	10	4.40	8.7-10
SA213 /A335	T91 / P91	140.00	6.00	12	1.92	10
SA213 /A335	T91 / P91	140.00	7.00	12	2.22	8-10
SA213 /A335	T91 / P91	140.00	10.00	18	4.47	6-10
SA213 /A335	T91 / P91	159.00	25.00	13	8.65	6.45
SA213 /A335	T91 / P91	168.00	30.00	9	6.58	7.47-8.31
SA213 /A335	T91 / P91	219.00	9.00	11	4.13	9.5-10.15
SA213 /A335	T91 / P91	273.00	45.00	4	8.06	7.47-8.31
SA213 /A335	T91 / P91	457.00	16.00	2	2.80	6.75-7.71

Chemical Composition & Mechanical Properties

Chemical Composition of ASTM A335 P91
Element	Composition (%)
Carbon (C)	0.08–0.12
Manganese (Mn)	0.30–0.60
Phosphorus (P)	≤0.02
Sulfur (S)	≤0.01
Silicon (Si)	0.20–0.50
Chromium (Cr)	8.00–9.50
Molybdenum (Mo)	0.85–1.05
Vanadium (V)	0.18–0.25
Niobium (Nb)	0.06–0.10
Nitrogen (N)	0.03–0.07

Mechanical Properties of ASTM A335 P91
Property	Value
Tensile Strength (MPa)	585 min
Yield Strength (MPa)	415 min
Elongation (%)	20 min
Hardness (HBW)	≤250

ASTM A335 P91 Type1 VS Type2
Grade	UNS Designation	Chemical Composition %
P91 Type 1	K91560	C	Mn	P	S	Si	Ni	Cr	Mo
		0.08-0.12	0.30-0.60	0.020	0.010	0.20-0.50	0.40 max	8.00-9.50	0.85-1.05
		V	N	Al	Cb	Ti	Zr	Sn	Sb
		0.18-0.25	0.030-0.070	0.02 max	0.06-010	0.01 max	0.01 max	_	_
P91 Type 2	K91560	C	Mn	P	S	Si	Ni	Cr	Mo
		0.08-0.12	0.30-0.50	0.020	0.005	0.20-0.40	0.40 max	8.00-9.50	0.85-1.05
		V	N	Al	Cb	Ti	Zr	Sn	Sb
		0.18-0.25	0.035-0.070	0.02 max	0.06-0.10	0.01 max	0.01 max	0.010 max	0.003 max

ASTM A335 P91 Type 1 & Type 2 have subtle differences mainly in elements Mn, S, Si, N, Sn and Sb content, and Type 2 has stricter requirements on element content than Type 1. P91 type 1 and 2 shall have a hardness within the range of 190 to 250 [HBW] or 196 to 265 [HV] or 91 HRBW to 25 HRC.

Advantages of ASTM A335 P91 Alloy Steel

P91 (9Cr-1Mo-V-Nb) is a high-performance ferritic alloy steel designed for high-temperature service in power plants and petrochemical systems.

High Temperature Strength

Maintains mechanical performance up to 600°C, allowing reduced wall thickness in steam piping and headers.

Oxidation Resistance

Withstands aggressive thermal and chemical environments, supporting advanced boiler design.

Thermal Fatigue Life

Offers up to 10× longer fatigue life compared to conventional steels, reducing shutdowns and failures.

Microstructure Stability

Requires controlled heat treatment to maintain tempered martensitic structure and creep strength.

Alloy Composition

Chromium, molybdenum, vanadium, and niobium enhance strength, oxidation resistance, and weldability.

Weldability & Applications

Widely used in superheaters, reheaters, HRSGs, and headers with compatible welding consumables.

P91 alloy steel has become the industry standard for high-efficiency power plant systems. It delivers exceptional performance in demanding thermal environments and is essential for systems operating under high pressure and temperature conditions.

ASTM A335 P91 is a seamless ferritic chrome moly alloy steel pipe used for high-temperature and anti-corrosion services. It contains 8.00–9.50% chromium and 0.85–1.05% molybdenum, with a minimum tensile strength of 415 MPa and yield strength of 205 MPa. It is commonly used in power plants, chemical plants, and other industrial facilities due to its excellent high-temperature strength and resistance to oxidation and corrosion.

ASTM A335/ASME SA335 Grade P91 is a ferritic alloy steel known for its high creep strength and resistance to thermal fatigue. Also referred to as 9Cr-1Mo steel, it is used in high-pressure, high-temperature environments such as boiler tubes, superheaters, and heat exchangers.

P91 Type 1 and Type 2 differ in chemical composition tolerances. Type 2 has stricter limits on elements like Mn, S, Si, N, Sn, and Sb. Both types share the same hardness range (190–250 HBW or 91 HRBW to 25 HRC) but are selected based on specific performance requirements.

P91 is a creep-strength-enhanced ferritic (CSEF) alloy steel made of 9% chromium and 1% molybdenum. It is designed to retain mechanical strength and stability at elevated temperatures, commonly used in high-temperature piping systems.

P91 (UNS K91560) is equivalent to the national standard 10Cr9Mo1VNb. It is a tempered martensitic heat-resistant steel containing elements like chromium, molybdenum, vanadium, and niobium, ensuring excellent thermal and mechanical performance.

P9 is a 9Cr-1Mo alloy steel suited for high-temperature service, while P91 includes additional elements like vanadium, niobium, and nitrogen to enhance creep resistance. P91 offers superior long-term performance under sustained high-temperature and pressure conditions.

P91 and T91 are essentially the same material. "P91" refers to seamless pipe under ASTM A335, while "T91" refers to tubing under ASTM A213. The difference lies in product form and specification, not the material itself.

P91 pipes come in various schedules and wall thicknesses ranging from 3 mm to 12 mm or more, depending on pipe diameter and pressure class. Custom thicknesses are also available to suit specific application requirements.

Industrial Applications

ASTM A335 chrome moly pipes are widely used in various industries due to their excellent mechanical properties and resistance to high temperatures.

Power Generation

Used in high-temperature and high-pressure boiler tubes, superheaters, and reheaters for efficient energy conversion.

Oil & Gas

Applied in refineries and petrochemical plants to transport high-temperature hydrocarbons.

Chemical Processing

Used in facilities handling corrosive and high-temperature fluids during various chemical reactions.

Nuclear Power

Employed in nuclear power plants for critical piping systems resistant to extreme heat and pressure.

Industrial Heating

Used in furnaces and heat exchangers due to excellent resistance to high temperature and thermal fatigue.

Steam Systems

Applied in high-pressure steam systems in industries like pulp and paper where thermal durability is essential.

ASTM A335 P91 Seamless Pipe

ASTM A335 P91 Seamless Pipe

ASTM A213 / A335 T91 / P91 Pipe Stock List

Chemical Composition & Mechanical Properties