Stainless Steel 304 Pipes | SS 304L and 304H, ASTM A312

Stainless steel 304 pipes come in three grades: 304, 304L, and 304H. All three are built on the same alloy of roughly 18% chromium and 8% nickel, and carbon is the only thing that changes. Plain 304 covers most water, food and general process work. If the pipe is going to be welded, SS 304L is the safer pick, as its lower carbon keeps the weld zone from corroding. SS 304H is for lines that run hot, above about 525°C, like steam and heater piping. Pipe comes to ASTM A312 as seamless, welded or EFW, in sizes from 1/8 to 24 inch NB. You can order all three grades from Metinox Overseas, a Mumbai based supplier of stainless steel pipe.

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Table of content

Stainless Steel 304 Pipe Tables
Types of SS 304, 304L and 304H Pipe: Seamless, Welded, and EFW
Frequently Asked Questions

What Is SS 304L - And How Does It Differ From 304 and 304H?

Point	SS 304	SS 304L	SS 304H
UNS	S30400	S30403	S30409
Carbon	0.08% max	0.035% max	0.04 to 0.10%
Grain size rule	None	None	ASTM No. 7 or coarser
Minimum tensile / yield	515 / 205 MPa	485 / 170 MPa	515 / 205 MPa
Weld zone corrosion risk	Some, if held between about 425 and 860 °C	Very low	Higher; not for wet corrosive service after welding
Best for	General service, unwelded or annealed lines	Welded water, food, pharma and chemical lines	Steam headers, boiler piping, refinery heaters above about 525 °C
Dual certification	304/304L common; 304/304H possible when carbon is 0.04 to 0.08%	304/304L	304/304H

Which grade to specify: welded lines in corrosive service 304L. High-temperature service under sustained load 304H. General unwelded service 304, or dual-certified 304/304L for added flexibility.

Stainless Steel 304 Pipes Specification: ASTM A312 and A358 for 304, 304L and 304H

Specification	Detail
Grades/ UNS	SS 304 (TP304, S30400), SS 304L (TP304L, S30403), SS 304H (TP304H, S30409)
Standard	ASTM A312 / ASME SA312; ASTM A358 / ASME SA358 for EFW
Dual certification	304/304L or 304/304H on request, meeting both grades in one heat
Types	Seamless, welded, ERW and EFW
Seamless pipe size	NPS 1/8 to 24
Welded and ERW pipe size	NPS 1/2 to 24
EFW pipe size	NPS 6 and above
Schedules	5S, 10S, 40S, 80S, 160, XS, XXS
Length	Single random, double random or cut to length
Pipe ends	Plain, bevelled, threaded on small bore
Finish	Solution annealed and pickled; polished on request
Tolerances	Wall up to 12.5% under nominal; OD per ASTM A999
Marking	Grade, size, schedule, heat number and ASTM A312 on every length
Certificates	EN 10204 3.1; 3.2 through an independent inspector on request

Buyer note: write the grade exactly on your purchase order. Ordering “304” or “304/304L” will not pull an H-grade heat. For 304H, add “grain size to be reported” to the purchase order.

What Is the Chemical Composition of 304 Stainless Steel per ASTM A312?

Element	TP304	TP304L	TP304H
Carbon (C)	0.08 max	0.035 max	0.04 to 0.10
Manganese (Mn)	2.00 max	2.00 max	2.00 max
Phosphorus (P)	0.045 max	0.045 max	0.045 max
Sulphur (S)	0.030 max	0.030 max	0.030 max
Silicon (Si)	1.00 max	1.00 max	1.00 max
Chromium (Cr)	18.0 to 20.0	18.0 to 20.0	18.0 to 20.0
Nickel (Ni)	8.0 to 11.0	8.0 to 13.0	8.0 to 11.0
Nitrogen (N)	0.10 max	0.10 max	n/a
Iron (Fe)	Balance	Balance	Balance

Buyer note: only the carbon line separates the three grades. A heat with carbon between 0.04 and 0.08% and the right grain size can be certified as both 304 and 304H; a heat at 0.035% or below can carry 304/304L.

Mechanical Properties of SS 304/304L/304H Pipes

304 is slightly stronger. 304L trades about 6% of its tensile strength and 17% of its yield for better welds. 304H matches 304 at room temperature and pulls ahead only when hot.

Property	TP304	TP304L	TP304H	Dual 304/304L
Tensile strength min	515 MPa	485 MPa	515 MPa	515 MPa
Yield strength min	205 MPa	170 MPa	205 MPa	205 MPa
Elongation in 50 mm, min	35% / 25%	35% / 25%	35% / 25%	35% / 25%
Hardness	No limit for pipe; 201 HB / 92 HRB max is the ASTM A240 plate limit, for reference only	Same	Same	Same

Which grade: for strength at room temperature, 304 or dual 304/304L; for strength at temperature, 304H.

Physical Properties of 304 Stainless Steel Pipe

Property	Value
Density	7.93 g/cm³ (0.286 lb/in³)
Melting range	1400 to 1450 °C
Elastic modulus	193 GPa (28.0 x 10⁶ psi)
Mean thermal expansion, 0 to 100 °C	17.2 µm/m·°C
Mean thermal expansion, 0 to 315 °C	17.8 µm/m·°C
Mean thermal expansion, 0 to 538 °C	18.4 µm/m·°C
Thermal conductivity at 100 °C	16.2 W/m·K
Thermal conductivity at 500 °C	21.5 W/m·K
Specific heat, 0 to 100 °C	500 J/kg·K
Electrical resistivity	0.72 µΩ·m
Magnetic response	Non-magnetic annealed; slightly magnetic after cold work

Buyer note: a 10m line heated from 20 to 538 °C grows by about 95 mm. Supports and loops need to allow for it.

Stainless Steel 304 Series Pipe- Equivalent Grades

Standard	304	304L	304H
ASTM / ASME	TP304 / SA312 TP304	TP304L / SA312 TP304L	TP304H / SA312 TP304H
UNS	S30400	S30403	S30409
EN / Werkstoff No.	1.4301 (X5CrNi18-10)	1.4307 (X2CrNi18-9); 1.4306 (X2CrNi19-11) is a close alternative with more nickel	1.4948 (X6CrNi18-10)
JIS	SUS304	SUS304L	SUS304H
BS	304S31	304S11 [	n/a

For tube, see our 304L tubes and 304H tubes.

Have a size list ready? Send it with grade, schedule, length and quantity through our quotation form and we will reply with a firm offer.

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SS 304L Pipe Material Specification in mm: Wall Thickness and Weight for 304, 304L and 304H

NPS	OD, mm	Sch 5S, kg/m	Sch 10S, kg/m	Sch 40S, kg/m	Sch 80S, kg/m	Sch 160, kg/m	XXS, kg/m
1/8	10.3	n/a	0.28	0.37	0.47	n/a	n/a
1/4	13.7	n/a	0.50	0.64	0.80	n/a	n/a
3/8	17.1	n/a	0.64	0.85	1.11	n/a	n/a
1/2	21.3	0.81	1.01	1.28	1.63	1.97	2.57
3/4	26.7	1.03	1.29	1.70	2.22	2.93	3.68
1	33.4	1.31	2.11	2.53	3.27	4.28	5.51
1 1/4	42.2	1.67	2.72	3.43	4.51	5.67	7.85
1 1/2	48.3	1.92	3.14	4.09	5.47	7.32	9.65
2	60.3	2.41	3.97	5.49	7.56	11.23	13.58
2 1/2	73.0	3.73	5.32	8.72	11.52	15.07	20.60
3	88.9	4.56	6.52	11.41	15.43	21.56	27.97
4	114.3	5.90	8.45	16.24	22.55	33.88	41.45
5	141.3	9.56	11.68	21.99	31.28	49.62	58.02
6	168.3	11.42	13.97	28.55	43.00	68.25	80.03
8	219.1	14.93	20.17	42.98	65.30	112.41	109.03
10	273.0	22.84	28.06	60.91	82.36	174.03	156.68
12	323.8	31.55	36.34	74.61	98.43	241.13	188.82

SS 304/304L/304H Seamless vs Welded vs EFW Pipe: Which One to Order

Point	Seamless	Welded / ERW	EFW
Standard	ASTM A312 / SA312	ASTM A312 / SA312	ASTM A358 / SA358
Made from	Solid billet	Rolled strip	Rolled plate
Wall	Wider variation when hot finished	Even and consistent	Follows plate thickness
Pressure and heat duty	Highest, the usual choice for 304H	Good for moderate pressure	Suits large process and header lines
Cost	Highest	Lower	Economical for large bore
Use	Steam, high pressure, small bore	Water, food, pharma, chemical	Large headers, flue gas, process lines

Which grade and form: 304L welded for most process lines; 304H seamless for hot, high pressure lines.

For higher temperatures or stabilised grades, see 321/321H pipe and 347/347H pipe.

Industrial Applications by Grade

Chemical plants usually order 304L for welded lines, because the low carbon protects the weld zone. A mill or stockist supplying chemical industry projects should offer intergranular corrosion testing to ASTM A262 Practice E, full heat traceability and dual certified 304/304L. Metinox Overseas supplies 304L pipe to these requirements.

Industry	304	304L	304H
Chemical	Mild chemicals, nitric acid service	Transporting chemicals and corrosive fluids in welded lines	Hot process lines where corrosion is mild
Food and beverage	Process and utility lines	Hygienic processing and fluid transfer	n/a
Pharmaceutical	Utility piping	Manufacturing and laboratory piping systems	n/a
Water treatment	Distribution	Filtration and water distribution plants	n/a
Oil and gas, petrochemical	Instrument and utility lines	Compatible fluid transportation and processing	Reactor effluent and hot process gas lines
Power generation	Cooling water	Condensate	Steam headers, steam lines and boiler piping
Refining	Utility	Process piping	Heater outlet and transfer lines, catalytic cracking flue gas and regenerator piping

Where chlorides are present (seawater, coastal air, brine), move up to 316/316L pipe.

Types of SS 304, 304L and 304H Pipe: Seamless, Welded, and EFW

The grade tells you what the steel is made of. The form tells you how the pipe was made, and that decides the size range, the wall control and the price. Each form below is available in 304, 304L and 304H.

304H Seamless Pipe

Made from a solid billet, so there is no seam along its length. The usual choice for high pressure, steam and small bore lines, and for most 304H work where the pipe runs hot under load. ASTM A312.

304H Welded Pipe

Formed from rolled strip, welded along its length and then solution annealed. Even wall and lower cost, which suits water, food, pharma and chemical lines. ASTM A312.

304H EFW Pipe

Formed from plate and fusion welded. For bores too large for strip mills, such as headers and large process lines. Large diameter stainless pipe is usually ordered this way. ASTM A358.

Frequently Asked Questions

SS 304L is the low carbon grade of 304 stainless steel, UNS S30403, with carbon limited to 0.035% max in ASTM A312 pipe. The low carbon protects welded joints from intergranular corrosion, which makes it the standard grade for welded stainless piping.

It is available in both forms, but seamless is the usual choice where the line runs hot under steady load. Check your piping code before choosing welded.

Welded pipe is usually the better value for water, food and process lines. Seamless makes sense for high pressure or small bore lines.

304 is slightly stronger. ASTM A312 sets 515 MPa tensile and 205 MPa yield minimums for 304, against 485 and 170 MPa for 304L. Dual certified 304/304L pipe meets the higher 304 values while keeping the low carbon of 304L.

For pipe, it is ASTM A312 grade TP304L (ASME SA312), with ASTM A358 for large diameter fusion welded pipe. Tube is made to ASTM A213, A249 or A269, and the UNS number is S30403.

Not always. Seamless pipe suits high pressure, heavy walls and small bore. Welded pipe to ASTM A312 is solution annealed and tested like seamless and costs less, which makes it the usual choice for water, food and process lines.

This page covers SS 304L pipe. Sheet and plate are made to ASTM A240 rather than A312; ask Metinox Overseas whether sheet and plate can be quoted with your pipe order.

Multiply the price per kg by the pipe’s weight per metre. For example, NPS 4 schedule 40S weighs about 16.24 kg/m, so the price per metre is 16.24 times the price per kg.

Send the grade, standard, OD, wall, length, quantity, end finish, certification, inspection, destination port and required date. Add the design temperature and your material specification if you have them.

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Stainless Steel 304 Pipes: Seamless, Welded and EFW in 304, 304L and 304H