ASTM A268 Stainless Steel Tubing are widely used in demanding industrial environments such as chemical processing, heat exchangers, boiler manufacturing, and high-temperature gas transportation due to their excellent corrosion resistance and high-temperature performance.  

ASTM A268 is a standard established by the American Society for Testing and Materials (ASTM), applicable to ferritic stainless steel seamless and welded tubes, primarily used for mechanical and industrial applications in corrosion-resistant and heat-resistant environments. This standard covers various grades of ferritic stainless steel, such as TP409, TP410, TP430, TP446, and others.

ASTM A268 Specification

Specifications	ASTM A268 / SA 268
Dimensions	ASTM, ASME and API
Size	1/4″ (6.25mm) to 8″ (203mm), WT 0.02″ (0.5mm) to 0.5″(12mm)
Schedule	SCH20, SCH30, SCH40, STD, SCH80, XS, SCH60, SCH80, SCH120, SCH140, SCH160, XXS
Specialized in	Large Diameter Size
Length	Single Random, Double Random & Cut Length.
Form	Round, Square, Rectangular, Hydraulic Etc
End	Plain End, Beveled End, Treaded

ASTM A268 Chemical Composition

Grade	TP 405	TP 410	TP 429	TP 430	TP 443	TP 446-1	TP 446-2A	…	TP 409
UNS	S40500	S41000	S42900	S43000	S44300	S44600	S44600	S40800	S40900
DesignationB
Element	Composition, %
C, max	0.18	0.15	0.12	0.12	0.2	0.2	0.12	0.08	0.08
Mn, max	1	1	1	1	1	1.5	1.5	1	1
P, max	0.04	0.04	0.04	0.04	0.04	0.04	0.04	0.045	0.045
S, max	0.03	0.03	0.03	0.03	0.03	0.03	0.03	0.045	0.045
Si, max	0.75	0.75	0.75	0.75	0.75	0.75	0.75	1	1
Ni	0.50max	0.50max	0.50max	0.50max	0.50max	0.50max	0.50max	0.80max	0.50max
Cr	11.5-13.5	11.5-13.5	14.0-16.0	16.0-18.0	18.0-23.0	23.0-30.0	23.0-30.0	11.5-13.0	10.50-11.75
Mo	…	…	…	…	…	…	…	…	…
Al	0.10-0.30	…	…	…	…	…	…	…	…
Cu	…	…	…	…	0.90-0.25	…	…	…	…
N	…	…	…	…	…	0.10-0.25	0.10-0.25	…	…
Ti	…	…	…	…	…	…	…	12xC min;	6xC min;
								1.10max	0.75max

ASTM A268 Tubing Mechanical Properties

Grade and UNS Designation	Tensile strength, min, ksi[MPa]	Yield strength, min, ksi[MPa]	ElongationA in 2 in or 50 mm, min,%
TP 405 S40500	30[415]	30[205]	20
… S40800	55[380]	30[205]	20
TP 410 S41000	60[415]	30[215]	20
TP 429, TP 430, and TP 430 Ti S429000, S43000, and S43036	60[415]	35[240]	20
TP 443 S44300	70[485]	40[275]	20
TP 446-1 S44600	70[485]	40[275]	18
TP 446-2 S44600	65[450]	40[275]	20
TP 409 S40900	55[380]	30[205]	20

Manufacturing Processes

The ASTM A268 standard covers ferritic and martensitic stainless steel tubes used for corrosion-resistant and high-temperature applications. It explicitly specifies two primary manufacturing processes: seamless tubes and welded tubes.

Seamless Tubes (Seamless)

ASTM A268 standard-compliant seamless stainless steel tubes are produced using an integral forming process. They are manufactured by heating and piercing stainless steel round billets, followed by hot rolling, cold rolling, and other processing steps. These tubes have no weld seams, resulting in more uniform wall thickness and more reliable corrosion resistance, particularly in harsh environments involving high pressure, high temperature, or corrosive media.

Welded tubes (Welded)

ASTM A268 welded stainless steeltubes, on the other hand, are made from stainless steel strips that are rolled into shape and then welded using processes such as high-frequency resistance welding or argon arc welding. They offer high production efficiency and relatively low costs, making them suitable for large-diameter, long-distance pipeline installations. Although welded seams are present, strict weld seam processing and inspection, such as grinding and polishing, ultrasonic testing, etc., ensure weld seam quality, enabling them to play a crucial role in low-pressure transportation and building structural support applications, such as low-pressure transportation pipelines for petroleum and natural gas, and handrails in building decorations.

ASTM A268 Stainless Steel Tubing Dimension

Stainless Steel Pipe (ASME B 36.19M)
Nominal Size		OD	Sch5s		Sch10s		Sch40s		Sch80s
DN	NPS	0	T	kg/m	T	kg/m	T	kg/m	T	kg/m
6	1/8	10.3			1.24	0.28	1.73	0.37	2.41	0.47
8	1/4	13.7			1.65	0.49	2.24	0.63	3.02	0.8
10	3/8	17.1			1.65	0.63	2.31	0.84	3.2	1.1
15	1/2	21.3	1.65	0.82	2.11	1	2.77	1.27	3.73	1.62
20	3/4	26.7	1.65	1.04	2.11	1.28	2.87	1.69	3.91	2.2
25	1	33.4	1.65	1.33	2.77	2.09	3.38	2.5	4.55	3.24
32	1 1/4	42.2	1.65	1.68	2.77	2.7	3.56	3.39	4.85	4.47
40	1 1/2	48.3	1.65	1.95	2.77	3.11	3.68	4.05	5.08	5.41
50	2	60.3	1.65	2.44	2.77	3.93	3.91	5.44	5.54	7.48
65	2 1/2	73.0	2.11	3.77	3.05	5.26	5.16	8.63	7.01	11.41
80	3	88.9	2.11	4.6	3.05	6.45	5.49	11.29	7.62	15.27
90	31/2	101.6	2.11	5.29	3.05	7.4	5.74	13.57	8.08	18.63
100	4	114.3	2.11	5.96	3.05	8.36	6.02	16.07	8.56	22.32
125	5	141.3	2.77	9.67	3.4	11.57	6.55	21.77	9.53	30.97
150	6	168.3	2.77	11.55	3.4	13.48	7.11	28.26	10.97	42.56
200	8	219.1	2.77	15.09	3.76	19.96	8.18	42.55	12.7	64.64
250	10	273.1	3.4	23.08	4.19	27.78	9.27	60.31	12.7	96.01
300	12	323.9	3.96	31.89	4.57	36	9.53	73.88	12.7	132.08
350	14	355.6	3.96	35.06	4.78	41.3
400	16	406.4	4.19	42.41	4.78	47.29
450	18	457.2	4.19	47.77	4.78	53.26

ASTM A268 Stainless Steel Tubing Tolerance

Outside Diameter, In.[Mm]	OD Tolerance, In.[Mm]	Wall Thickness, %	Thin Wall Tubes
Up To1⁄2, [12.7], Excl	±0.005 [0.13]	±15
1⁄2 To 11⁄2 [12.7 To 38.1], Excl/Td>	±0.005 [0.13]	±10<	Less Than 0.065 In. [1.6 Mm] Nominal
11⁄2 To 31⁄2 [38.1 To 88.9], Excl	±0.010 [0.25]	±10	Less Than 0.095 In. [2.4 Mm] Nominal
31⁄2 To 51⁄2 [88.9 To 139.7], Excl	±0.015 [0.38]	±10	Less Than 0.150 In. [3.8 Mm] Nominal
51⁄2 To 8 [139.7 To 203.2], Incl	±0.030 [0.76]	±10	Less Than 0.150 In. [3.8 Mm] Nominal

Why is ASTM A268 stainless steel tubing so popular?

Outstanding corrosion resistance

The steel grades covered by ASTM A268, such as TP410 and TP430, are primarily ferritic or martensitic stainless steels, making them particularly suitable for environments containing chlorides, acidic gases, or other corrosive media. These materials exhibit strong resistance to pitting corrosion and stress corrosion cracking, enabling them to operate reliably and stably for extended periods even in marine, chemical, or humid environments, thereby preventing severe corrosion issues such as crevice corrosion and significantly enhancing system reliability and service life.

Excellent high-temperature performance

ASTM A268 steel tubes maintain good performance in high-temperature environments, with their alloy composition providing excellent oxidation resistance and thermal stability. Even under continuous high-temperature operating conditions, they retain good mechanical strength and structural integrity, making them commonly used in high-temperature equipment such as heat exchangers, furnace tubes, and exhaust systems.

High strength and excellent wear resistance

Especially martensitic grades like TP410, which can significantly enhance hardness and strength after heat treatment. This makes them ideal for environments requiring high pressure or frequent wear, widely used in boiler systems, energy equipment, and various mechanical structures.

Excellent machinability and flexible installation

In addition to its superior performance, ASTM A268 stainless steel tubing offers excellent machinability, supporting conventional cutting, bending, welding, and forming processes.

 Application Areas

Petroleum refining equipment and heating furnace pipes

Heat exchangers and condenser tubes

Industrial boilers and flue gas systems

Chemical processing equipment

Automotive exhaust systems and exhaust gas recovery systems

Heating systems in the paper and textile industries

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