What is difference between ASTM A312 TP304 and TP316?
Jun 03, 2026
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What is ASTM A312 TP304 stainless steel round pipe?
ASTM A312 TP304 stainless steel round pipe is the most widely utilized specification, specifically designated for the manufacture of seamless, welded, and heavily cold-worked austenitic stainless steel piping intended for use in high-temperature and general corrosive service environments. This piping material is produced from the TP304 alloy (UNS S30400)-the standard "18/8" stainless steel (containing 18% chromium and 8% nickel)-and features excellent formability, weldability, and good resistance to oxidation and mild corrosion.
What Is ASTM A312 TP316 Stainless Steel Pipe?
ASTM A312 TP316 is a standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipes intended for high-temperature and general corrosive service.
It is manufactured from TP316 alloy (UNS S31600), often called "marine grade" stainless steel. Its defining feature is the addition of 2.0–3.0% Molybdenum, which provides superior resistance to pitting and crevice corrosion in chloride environments (e.g., seawater, coastal air, chemical processing) compared to TP304.
What is difference between ASTM A312 TP304 and TP316?
ASTM A312 TP304 and TP316 both define seamless or welded austenitic stainless steel pipes, but they differ primarily in their chemical composition. TP316 contains molybdenum (2-3%), which gives it far superior corrosion and pitting resistance against chlorides and marine environments compared to TP304.
ASTM A312 TP304 vs. TP316: Chemical Composition
| Grade | C (max) | Mn (max) | P (max) | S (max) | Si (max) | Cr | Ni | Mo |
| TP304 | 0.08% | 2.00% | 0.045% | 0.030% | 1.00% | 18.0–20.0% | 8.0–11.0% | - |
| TP316 | 0.08% | 2.00% | 0.045% | 0.030% | 1.00% | 16.0–18.0% | 11.0–14.0% | 2.0–3.0% |
ASTM A312 TP304 vs. TP316: Mechanical Properties
| Grade | Tensile Strength, min | Yield Strength, min | Elongation in 2 in. (50mm), min |
| TP304 | 75 ksi (515 MPa) | 30 ksi (205 MPa) | 35% |
| TP316 | 75 ksi (515 MPa) | 30 ksi (205 MPa) | 35% |
Nominal wall thickness for ASTM A312(Seamless and straight seame welded steel pipes)
| NPS | ASTM A312 WT Tolerance, % | |
|---|---|---|
| + | – | |
| 1/8-2 1 /2 | 20.0 | 12.5 |
| 3~18, t/D≤ 5% | 22.5 | 12.5 |
| 3~18, t/D> 5% | 15.0 | 12.5 |
| ≥ 20, welded | 17.5 | 12.5 |
| ≥ 20, seamless, t/D≤ 5% | 22.5 | 12.5 |
| ≥ 20, seamless, t/D> 5% | 15.0 | 12.5 |
ASTM A312 Stainless Steel Pipes OD Tolerance
| NPS | ASTM A312 OD Tolerance | |||
|---|---|---|---|---|
| + | – | |||
| inch | mm | inch | mm | |
| 1/8~1 1 /2 > 1 1 /2~4 > 4~8 > 8~18 > 18~26 > 26~34 > 34~48 |
1/64(0.015) 1/32(0.031) 1/16(0.062) 3/32(0.093) 1/8(0.125) 5/32(0.156) 3/16(0.187) |
0.4 0.8 1.6 2.4 3.2 4.0 4.8 |
1/32(0.031) 1/32(0.031) 1/32(0.031) 1/32(0.031) 1/32(0.031) 1/32(0.031) 1/32(0.031) |
0.8 0.8 0.8 0.8 0.8 0.8 0.8 |
ASTM A312 TP304 vs. TP316: Corrosion Resistance
In terms of corrosion resistance, TP316 significantly outperforms TP304, particularly in environments containing chlorides and acidic media. TP304 is more susceptible to pitting corrosion and crevice corrosion, whereas TP316 contains 2–3% molybdenum (Mo), which helps form a more stable passive film on the stainless steel surface, thereby substantially enhancing its resistance to both pitting and crevice corrosion. The Pitting Resistance Equivalent Number (PREN) is commonly used to evaluate a stainless steel's resistance to pitting corrosion, with higher values indicating better corrosion resistance. TP304 typically has a PREN value of approximately 18–20, while TP316 generally achieves a PREN value of 23–28, representing an improvement in pitting corrosion resistance of about 20%–40%.
Why is TP316 more expensive than TP304?
The price of 316 stainless steel is typically 10% to 30% higher than that of 304 stainless steel. TP316 is more expensive because it contains molybdenum and requires a higher nickel content than 304. In terms of raw material costs, 304 stainless steel generally ranges from $3.50 to $5.00 per kilogram, while the price range for 316 stainless steel is $4.50 to $6.50 per kilogram.
TP304 vs. TP316: Which Is Better Suited for High-Temperature ?
Under intermittent service conditions, both grades can be utilized in environments reaching temperatures of up to approximately 870°C (1600°F). However, if the application involves continuous operation within the 425–860°C range, it is recommended to prioritize "L" series grades (such as TP304L or TP316L) to prevent carbide precipitation, or to select "H" series grades to achieve superior high-temperature strength.
ASTM A312 TP304 vs. TP316: Applications
TP304：Water pipes, food processing equipment, sinks, architectural decorative components.
TP316: Chemical processing, marine engineering, pharmaceutical piping, coastal structures.
ASTM A312 TP304 / TP316 Stainless Steel Pipe Supplier
We maintain a ready stock of standard specifications (SCH 10S, SCH 40S) in TP304 and TP316 grades, enabling immediate shipment within 7 to 15 days.
Custom Processing: We offer a range of value-added services, including precision cutting, pipe bending, beveling, drilling, and professional surface finishing (mirror/brushed).
| Product Type | Grade | Outside Diameter (OD) | Wall Thickness (WT) | Length | End Finish |
| Seamless Pipe | TP304/304L, TP316/316L | 1/8" to 30" (DN6 - DN750) | SCH 5S, 10S, 40S, 80S, 160, XXS | 5.8m, 6m, 11.8m, 12m or Custom | Plain, Beveled, Threaded |
| Welded Pipe | TP304/304L, TP316/316L | 1/2" to 80" (DN15 - DN2000) | SCH 5S, 10S, 40S, 80S | Single/Double Random, or Fixed | Plain, Beveled |
| Surface Finish | TP304 / TP316 |
Pickled, Annealed, 2B, BA, No.4, 400/600/800 Mirror Polish |
We provide Material Test Certificates (MTC) in accordance with the EN 10204 3.1 standard. We conduct hydrostatic testing, eddy current testing, ultrasonic testing, and PMI (Positive Material Identification) to ensure that the chemical composition (Ni, Cr, Mo) complies with the ASTM A312 standard.
Packaging: We utilize standard-compliant export packaging suitable for sea freight (wooden crates, reinforced steel frame crates, or protective plastic end caps).
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