ASTM A312 304 Steel Pipe: Specification and Applications

ASTM A312 304 Steel Pipe is a seamless or welded austenitic stainless steel pipe with the designation 304, manufactured in strict accordance with the ASTM A312/A312M standard.

ASTM A312 is an internationally recognized standard specification for seamless, welded, and heavily cold-worked welded austenitic stainless steel pipe for use in high-temperature and generally corrosive applications. UNS S30400 is the most commonly used grade of austenitic stainless steel, characterized by a content of approximately 18% chromium and 8% nickel. It offers excellent corrosion resistance, good mechanical properties, and exceptional workability and weldability.

ASTM A312 304 Steel Pipe

Thus, the "ASTM A312 304 Steel Pipe" specifically refers to this type of 304 stainless steel pipe material whose chemical composition and mechanical properties meet the requirements of ASTM A312 and is suitable for use in high-pressure and general corrosive media transportation systems.

Below is a table listing common Nominal Pipe Sizes (NPS) and their corresponding standard dimensions for seamless or welded ASTM A312 TP304 pipe.

Nominal Pipe Size (NPS)	Outside Diameter (OD) [Inches]	Outside Diameter (OD) [mm]	Schedule (SCH)	Wall Thickness (WT) [Inches]	Wall Thickness (WT) [mm]
1/2	0.840	21.3	5S	0.065	1.65
			10S	0.083	2.11
			40S	0.109	2.77
			80S	0.147	3.73
1	1.315	33.4	5S	0.065	1.65
			10S	0.109	2.77
			40S	0.133	3.38
			80S	0.179	4.55
2	2.375	60.3	5S	0.065	1.65
			10S	0.109	2.77
			40S	0.154	3.91
			80S	0.218	5.54
4	4.500	114.3	5S	0.083	2.11
			10S	0.120	3.05
			40S	0.237	6.02
			80S	0.337	8.56
6	6.625	168.3	5S	0.109	2.77
			10S	0.134	3.40
			40S	0.280	7.11
			80S	0.432	10.97
8	8.625	219.1	5S	0.109	2.77
			10S	0.148	3.76
			40S	0.322	8.18
			80S	0.500	12.70

ASTM A312 TP304 stainless steel pipe covers chemical composition, mechanical properties and manufacturing requirements.

Composition	TP304 (UNS S30400)
Carbon, C	≤0.08
Chromium, Cr	18.0-20.0
Nickel, Ni	8.0-11.0
Manganese, Mn	≤2.00
Silicon, Si	≤1.00
Phosphorus, P	≤0.045
Sulfur, S	≤0.030
Molybdenum, Mo	-
Nitrogen, N	≤0.10
Iron, Fe	Balance

Mechanical Property	Value	SI Value	Testing Standard
Tensile Strength	≥ 75 ksi	≥515 MPa	ASTM A370
Yield Strength	≥ 30 ksi	≥205 MPa	ASTM A370
Elongation in 2 in. or 50 mm	≥35	≥35%	ASTM A370
Brinell Hardness	201 HBW	≤201	ASTM E10
Rockwell Hardness	92 HRW	≤92	ASTM E18

Physical Property	Value
Density	8.0 g/cm³
Melting Range	1399 - 1454℃
Specific Heat	0.50 J (g·℃)
Electrical Resistivity	7.2 x 10^-7Ω·m
Relative Magnetic Permeability	1.003
Modulus of Elasticity, E	193 GPa

Thermal Property	Temperature Range [∘C]	Value
Mean Coefficient of Thermal Expansion	20 - 100	17.2 µm/(m·℃)
	20 - 300	17.8 µm/(m·℃)
	20 - 500	18.4 µm/(m·℃)
Thermal Conductivity	20	16.2 W/(m·℃)
	100	16.3 W/(m·℃)
	500	21.5 W/(m·℃)

Food and Beverage Processing Industry

Transportation piping, dairy lines, beer fermentation tank and storage tank connections, and sanitary fluid transfer systems.

304 steel offers excellent non-toxicity and resistance to food acids and alkalis. It is easy to clean and sterilize, and remains stable during high-temperature sterilization, meeting stringent hygiene standards.

Chemical and Petrochemical Industries

Low- to medium-pressure fluid and gas transmission pipelines, tank connections, reactor piping, and non-critical heat exchanger tubing.

Suitable for processes handling a variety of mildly corrosive media. Its high strength and excellent weldability meet the safety and durability requirements of petrochemical piping systems.

Water Treatment and Supply Systems

Pipes and equipment connections in municipal water supply mains, high-purity water systems, and water treatment plants.

304 steel effectively resists chloride and microbial corrosion in freshwater and municipal water supplies, ensuring clean water quality and providing a long service life, preventing rusting of carbon steel pipes.

ASTM A312 304 Steel Pipe Applications

Construction and Decoration Engineering

Building structural supports, handrails, curtain wall support structures, public facilities, and decorative piping for environmental art.

304 stainless steel pipe offers excellent aesthetics, atmospheric corrosion resistance, and a high strength-to-weight ratio. When exposed to mild atmospheric conditions, it maintains a smooth surface for a long time, reducing maintenance requirements.

Industrial and Mechanical Manufacturing

Machinery frames, textile printing and dyeing equipment piping, papermaking industry pipelines, and various general industrial fluid transport applications.

As a general-purpose engineering material, 304 steel's excellent workability and weldability make it an economical choice for piping in various industrial equipment and auxiliary systems.

Why Is ASTM A312 304 Steel Pipe So Popular

Excellent Corrosion and Heat Resistance

304 stainless steel pipe contains approximately 18% chromium and 8% nickel, forming a strong austenitic structure. Chromium forms a chromium oxide passivation film on the steel surface, providing excellent resistance to atmospheric corrosion, oxidation, and corrosion in a variety of mild media.

It also exhibits excellent high-temperature oxidation resistance and can be used at temperatures up to 870°C, making it suitable for high-temperature auxiliary systems such as heat exchangers and boilers.

Excellent Machinability

As a typical austenitic stainless steel, 304 steel pipe exhibits excellent cold formability and deep drawing properties. It can be easily produced into seamless pipes of various sizes and wall thicknesses through cold drawing or cold rolling, or welded pipes through welding.

It also exhibits excellent weldability and can be joined using most standard welding methods, with post-weld annealing generally not required. Its high toughness and moderate strength meet the basic requirements of customers.

Excellent Machinability

Cost Advantage

Among all austenitic stainless steels, 304 grade has the most moderate nickel content and the highest production volume, offering significant advantages in raw material costs.

Compared to other high-alloy, high-corrosion-resistant steel grades, 304 steel pipe has a lower procurement cost.

Wide Range Industrial Applications

304 stainless steel pipe is a versatile material across multiple industries.

It is widely used in food hygiene, medical devices, chemical containers and piping, building structures, and household appliances. Its compliance with international standards such as ASTM A312 ensures standardization and interoperability across the global supply chain.