ASTM A335 Alloy Seamless Steel Pipes

Quantity:

Contact Now

add to cart

ASTM A335 is a standard specification for seamless ferritic alloy-steel pipes designed for high-temperature service. These pipes are manufactured from chromium-molybdenum (Cr-Mo) alloy steels, which provide enhanced strength, resistance to oxidation (scaling), and creep resistance at elevated temperatures compared to carbon steel pipes. Common grades include P5 (5Cr-0.5Mo), P9 (9Cr-1Mo), P11 (1.25Cr-0.5Mo), P22 (2.25Cr-1Mo), and P91 (9Cr-1Mo-V). The seamless construction ensures reliability under high pressure and temperature conditions.

Primarily used in power generation boilers, refineries, petrochemical plants, and high-pressure process piping systems, ASTM A335 pipes handle critical applications such as steam lines, superheaters, heat exchangers, and hydrocarbon processing units. They operate effectively in temperatures ranging from 400°C to 650°C+ (depending on grade). The standard mandates strict requirements for chemical composition, heat treatment (normalization/tempering), mechanical properties (tensile/yield strength), hydrostatic testing, and non-destructive examination to ensure performance in demanding environments where corrosion, thermal stress, and pressure are major concerns.

Chemical Composition

	Grade	P-5	P-9	P-11	P-22	P-91	P-91 shall also include the following:
Element	UNS Designation	K41545	S50400	K11597	K21590	K91560
Carbon	0.15 max	0.15 max	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 – 0.60	0.30 – 0.60	N at 0.030 – 0.070
Phosphorous, max	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	0.01	Al at 0.02 max
Silicon	0.50 max	0.25 – 1.00	0.50 – 1.00	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	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	0.87 – 1.13	0.85 – 1.05	Zr at 0.01 max

TensileTest

	Seamless
	P-5	P-9	P-11	P-22	P-91	P91 shall not have a hardness not exceeding 250 HB/265 HV [25HRC].
Tensile Strength, min., psi
ksi	60	60	60	60	85
MPa	415	415	415	415	585
Yield Strength, min., psi
ksi	30	30	30	30	60
MPa	205	205	205	205	415

Other Mechanical Test

Transverse or Longitudinal Tension Test and Flattening Test, Hardness Test, or Bend Test
For material heat treated in a batch-type furnace, tests shall be made on 5% of the pipe from each treated lot. for small lots, at least one pipe shall be tested.
For material heat treated by the continuous process, tests shall be made on a sufficient number of pipe to constitute 5% of the lot, but in no case less than 2 pipe.
Notes for Hardness Test:	P91 shall not have a hardness not exceeding 250 HB/265 HV [25HRC].
Notes for Bend Test:	For pipe whose diameter exceeds NPS 25 and whose diameter to wall thickness ratio is 7.0 or less shall be subjected to the bend test instead of the flattening test.
	Other pipe whose diameter equals or exceeds NPS 10 may be given the bend test in place of the flattening test subject to the approval of the purchaser.
	The bend test specimens shall be bent at room temperature through 180 without cracking on the outside of the bent portion.
	The inside diameter of the bend shall be 1 inch [25 mm].
Hydrostatic test	Each length of pipe shall be Hydro tested, at option of manufacture, nondestructive electric testing can be used.

Heat Treatment

	P5, P9, P11, and P22
Grade	Heat Treatment Type	Normalizing Temperature Range F [C]	Subcritical Annealing or Tempering Temperature Range F [C]
Grade	Heat Treatment Type	Normalizing Temperature Range F [C]
P5 (b,c)	Full or Isothermal Anneal
	Normalize and Temper	*****	1250 [675]
	Subcritical Anneal (P5c only)	*****	1325 – 1375 [715 – 745]
P9	Full or Isothermal Anneal
P9	Normalize and Temper	*****	1250 [675]
P11	Full or Isothermal Anneal
P11	Normalize and Temper	*****	1200 [650]
P22	Full or Isothermal Anneal
P22	Normalize and Temper	*****	1250 [675]
P91	Normalize and Temper	1900-1975 [1040 – 1080]	1350-1470 [730 – 800]
P91	Quench and Temper	1900-1975 [1040 – 1080]	1350-1470 [730 – 800]

Permissible Variation in Wall Thickness

NPS [DN] Designator	Tolerance, % from Specified
NPS [DN] Designator	Over	Under
1/8 to 2 1/2 [6 to 65] incl., all t/D ratios	20.00%	12.50%
Above 2 1/2 [65], t/D or = 5%	22.50%	12.50%
Above 2 1/2 [65], t/D 5%	15.00%	12.50%
(t = Specified Wall Thickness; D = Specified Outside Diameter)

Elongation Requirement

Calculated Minimum Elongation Values
Elongation in 2 in. or 50 mm, min %
Wall Thickness		P5, P9, P11, P22		P91
in.	mm	Longitudinal	Transverse	Longitudinal
5/16 (0.312)	8	30	20	20
9/32 (0.281)	7.2	28	19	19
1/4 (0.250)	6.4	27	18	18
7/32 (0.219)	5.6	26		17
3/16 (0.188)	4.8	24		16
5/32 (0.156)	4	22		15
7/8 (0.125)	3.2	21		14
3/32 (0.094)	2.4	20		13
1/18 (0.062)	1.6	18		12

Permissible Variations in Outside Diameter

NPS [DN] Designator	Over		Under
NPS [DN] Designator	in.	mm	in.	mm
1/8 to 1 1/2 [6 to 40], incl.	1/64 (0.015)	0.4	1/64 (0.015)	0.4
Over 1 1/2 to 4 [40 to 100], incl.	1/32 (0.031)	0.79	1/32 (0.031)	0.79
Over 4 to 8 [100 to 200], incl.	1/16 (0.062)	1.59	1/32 (0.031)	0.79
Over 8 to 12 [200 to 300], incl.	3/32 (0.093)	2.38	1/32 (0.031)	0.79
Over 12 [300]	+/- 1% of the specified outside diameter

Recommend Products

CONTACT US

Subscribe to our newsletter to receive the latest information