What Material Is ASTM A312 TP304 Stainless Steel Pipe?

What Is ASTM A312 TP304?

ASTM A312 TP304 is austenitic stainless steel pipe made from the Type 304 chemistry and produced under the ASTM A312 specification. The TP prefix identifies the pipe grade, and 304 identifies the 18% chromium, 8% nickel austenitic stainless steel that is the most widely used stainless material in the world.

A312 itself covers seamless, welded and heavily cold worked austenitic pipe for high-temperature and general corrosive service. It sets the chemical composition, mechanical properties, manufacturing route, heat treatment and testing requirements that a TP304 pipe must satisfy.

Chemical Composition of ASTM A312 TP304

Element	Content (%)
Chromium (Cr)	18.0 - 20.0
Nickel (Ni)	8.0 - 11.0
Carbon (C)	0.08 max
Manganese (Mn)	2.00 max
Silicon (Si)	1.00 max
Phosphorus (P)	0.045 max
Sulfur (S)	0.030 max
Iron (Fe)	Balance

Chromium forms the passive oxide film that gives the grade its corrosion resistance, while nickel stabilises the austenitic structure and keeps the pipe ductile and tough at low temperature. The grade contains no deliberate molybdenum addition, which is the main chemical difference from TP316.

Mechanical Properties of ASTM A312 TP304

Property	Requirement
Tensile strength	515 MPa (75 ksi) minimum
Yield strength, 0.2% offset	205 MPa (30 ksi) minimum
Elongation in 2 in. or 50 mm	35% minimum
Hardness	90 HRB maximum

Pipe is supplied in the solution annealed condition so that the microstructure is uniform and the specified elongation is achieved. Because austenitic stainless steel work hardens rapidly, cold bending, drawing or heavy machining raises strength and reduces ductility in the affected zone.

TP304, TP304L and TP316 Compared

TP304: standard carbon, the general-purpose choice for corrosion resistance, strength and weldability

TP304L: carbon capped at 0.030% to resist sensitisation in welded assemblies; slightly lower minimum strength

TP316: contains 2 - 3% molybdenum, improving resistance to pitting and crevice corrosion in chloride environments

TP316L: combines the molybdenum addition with low carbon for welded chloride service such as marine and process plant

In practice, TP304 is the cost-effective selection for general service, while the molybdenum-bearing grades are specified where chlorides, acids or seawater exposure are present.

Applications and Trade Codes for TP304 Pipe

Heat exchangers and condenser tubing

Food processing and dairy equipment

Chemical transport and processing lines

Water pipelines and sanitation systems

Architectural and structural piping, handrails and supports

Pulp and paper process piping

For customs classification, stainless steel pipe of this type falls under HS heading 7304 for seamless product, with 73044100 covering seamless stainless steel tubes, pipes and hollow profiles, and 73044900 covering the welded equivalent. Classification depends on the actual manufacturing route and on national tariff schedules, so the final code should be confirmed with the customs broker for the destination country.

FAQ: ASTM A312 TP304 Pipe

Q: What does TP304 mean in ASTM A312 TP304?
TP stands for tube or pipe grade and 304 identifies the 18% chromium, 8% nickel austenitic stainless steel chemistry used for the pipe.

Q: Is ASTM A312 TP304 the same as 304 stainless steel?
The material is the 304 chemistry. A312 adds the pipe-specific requirements for manufacturing, heat treatment, dimensions and testing, so a compliant pipe is more than just 304 material.

Q: What is the difference between TP304 and TP316?
TP304 contains no molybdenum, while TP316 includes 2 - 3% molybdenum that improves resistance to pitting in chloride environments. TP304 remains the lower-cost general-purpose option.

Q: Is TP304 pipe magnetic?
Annealed austenitic pipe is essentially non-magnetic. Cold working, welding or forming can create a slight magnetic response, which is normal for the grade.

Q: What is the maximum service temperature for TP304 pipe?
It handles a wide range of elevated-temperature service, but continuous operation in the carbide precipitation range should be avoided; for sustained high-temperature or welded service, the L or stabilised grades are preferred.

Q: What is the HS code for ASTM A312 TP304 pipe?
Seamless stainless steel pipe is normally classified under 73044100 and welded stainless steel pipe under 73044900. Codes vary by country and should be confirmed locally.