Standard Overview
ASTM A312 TP304 Schedule 40 stainless steel pipe is one of the most widely specified austenitic stainless steel pipes for industrial piping systems worldwide. Manufactured in accordance with ASTM International standard ASTM A312, TP304 (UNS S30400) SCH 40 pipe offers excellent corrosion resistance, strong mechanical performance, and reliable weldability for oil & gas, chemical processing, water treatment, and construction applications. Available in seamless and welded types, 304 Schedule 40 stainless steel pipe is a cost-effective solution for medium-pressure and general corrosive service environments, making it a preferred choice for global B2B buyers and EPC contractors.
Xi'an Dongmeng Group Co., Ltd. supplies ASTM A312 / ASME SA312 SCH 40 stainless steel pipe in TP304, TP304L, TP316, TP316L and other stainless steel grades. Products are available in seamless and welded types, with custom cutting, beveling, polishing, passivation, inspection certificates and seaworthy export packing.
ASTM A312 TP304 Schedule 40 stainless steel pipe is a widely used austenitic stainless steel pipe designed for high-temperature and general corrosive service. It is manufactured according to the requirements of ASTM International under the ASTM A312 / A312M specification.
Standard: ASTM A312 / A312M
Grade: TP304 (UNS S30400)
Pipe Schedule: SCH 40
Dimension Standard: ASME B36.19M
Manufacturing Type: Seamless (SMLS) or Welded (WLD)
Inspection Certificate: EN 10204 3.1 / 3.2 available
TP304 is one of the most demanded stainless steel grades in global industrial piping systems due to its excellent corrosion resistance, durability, and cost-performance ratio.
What Is TP304 Stainless Steel?
TP304 is an 18-8 austenitic stainless steel containing approximately:
18–20% Chromium
8–11% Nickel
This composition provides strong resistance to oxidation and corrosion in atmospheric, water, and mild chemical environments. It is non-magnetic in annealed condition and offers excellent weldability without requiring preheating.
Chemical Composition (ASTM A312 TP304)
| Element | Content (%) |
|---|---|
| C | ≤ 0.08 |
| Mn | ≤ 2.00 |
| Si | ≤ 1.00 |
| P | ≤ 0.045 |
| S | ≤ 0.030 |
| Cr | 18.0 – 20.0 |
| Ni | 8.0 – 11.0 |
| N | ≤ 0.10 |
Mechanical Properties
| Property | Minimum Value |
|---|---|
| Tensile Strength | 515 MPa |
| Yield Strength | 205 MPa |
| Elongation | 35% |
| Hardness | ≤ 201 HB |
TP304 maintains good toughness at both low and moderately high temperatures.
Schedule 40 Thickness Explained
"Schedule 40" refers to the wall thickness classification defined by ASME B36.19M for stainless steel pipes.
Examples:
| NPS | OD (mm) | Wall Thickness (mm) | Wall Thickness (inch) |
|---|---|---|---|
| 1" | 33.40 | 3.38 | 0.133" |
| 2" | 60.33 | 3.91 | 0.154" |
| 4" | 114.30 | 6.02 | 0.237" |
| 6" | 168.28 | 7.11 | 0.280" |
Schedule 40 offers a balanced wall thickness suitable for medium-pressure industrial systems.
Manufacturing Process
ASTM A312 TP304 pipes can be produced by:
1️⃣ Seamless Pipe
Billet piercing
Hot rolling or cold drawing
Solution annealing
Pickling or bright annealing
2️⃣ Welded Pipe
Stainless steel strip forming
Automatic TIG or laser welding
Heat treatment
Non-destructive testing (UT / RT / Eddy current)
Seamless pipes are preferred for high-pressure service, while welded pipes provide a more economical option for structural and low-pressure applications.
Corrosion Resistance Performance
TP304 offers:
Excellent resistance to atmospheric corrosion
Good resistance to fresh water and mild chemicals
Strong oxidation resistance up to 870°C (intermittent service)
However, it is not recommended for chloride-rich marine environments where pitting corrosion may occur. In such cases, TP316 may be more suitable.
Major Applications
🏭 Oil & Gas Industry
Process piping systems
Refinery transfer lines
Instrumentation tubing
🧪 Chemical Industry
Acid transport pipelines
Heat exchangers
Reactor piping
💧 Water Treatment
Desalination pre-treatment systems
Industrial water pipelines
🍽 Food & Beverage
Hygienic piping systems
Milk and beverage production lines
🏗 Construction & Infrastructure
Structural piping
Decorative exposed stainless steel systems
Fire protection lines
Advantages of TP304 Schedule 40 Pipe
✔ Excellent corrosion resistance
✔ Good mechanical strength
✔ Easy fabrication and welding
✔ Hygienic and easy to clean
✔ Globally standardized dimensions
✔ Cost-effective for large industrial projects
Quality Control & Testing
Professional manufacturers typically provide:
Spectrometer chemical analysis
Tensile & flattening test
Hydrostatic pressure test
PMI (Positive Material Identification)
Ultrasonic testing (UT)
Radiographic testing (RT)
Third-party inspection (SGS, BV, TUV)
Full traceability with heat number marking is standard for export projects.
TP304 vs TP304L – Quick Comparison
| Item | TP304 | TP304L |
|---|---|---|
| Carbon Content | ≤ 0.08% | ≤ 0.03% |
| Weld Corrosion Risk | Moderate | Lower |
| Intergranular Corrosion Resistance | Good | Better |
| Cost | Slightly lower | Slightly higher |
TP304L is recommended for heavy welding projects or critical corrosion environments.
FAQ
1️⃣ What is ASTM A312 TP304 Schedule 40 stainless steel pipe?
ASTM A312 TP304 Schedule 40 pipe is an austenitic stainless steel pipe manufactured according to the standard issued by ASTM International. It is designed for high-temperature and general corrosive service, with Schedule 40 referring to a standardized wall thickness under ASME B36.19M.
2️⃣ What is the difference between TP304 and TP304L?
The main difference is carbon content:
TP304: ≤ 0.08% carbon
TP304L: ≤ 0.03% carbon
TP304L offers better resistance to intergranular corrosion after welding. For heavy welding or critical chemical systems, TP304L is generally recommended.
3️⃣ What does Schedule 40 mean in stainless steel pipes?
Schedule 40 (SCH 40) defines the wall thickness of the pipe. It affects:
Pressure rating
Weight per meter
Mechanical strength
For example, a 2-inch TP304 SCH 40 pipe has a wall thickness of approximately 3.91 mm (0.154 inch).
4️⃣ Is TP304 Schedule 40 pipe suitable for oil and gas applications?
Yes, it is commonly used in:
Low to medium-pressure process piping
Refinery transfer lines
Instrumentation systems
However, for high chloride or offshore environments, TP316 may be more suitable due to improved pitting resistance.
5️⃣ What are the available manufacturing types?
ASTM A312 TP304 pipes are available as:
Seamless (SMLS)
Welded (WLD)
Cold worked
Seamless pipes are preferred for high-pressure systems, while welded pipes offer a cost-effective solution for structural or low-pressure use.
6️⃣ What certifications are typically provided for export?
Professional manufacturers usually provide:
EN 10204 3.1 MTC
PMI (Positive Material Identification) report
Hydrostatic test report
Third-party inspection (SGS / BV / TUV upon request)
This ensures full traceability and compliance for international EPC projects.
7️⃣ What industries commonly use TP304 Schedule 40 pipes?
Major industries include:
Oil & Gas
Chemical processing
Water treatment
Food & beverage
Power generation
Construction & infrastructure
Its corrosion resistance and fabrication performance make it highly versatile.
8️⃣ What temperature range can TP304 withstand?
TP304 stainless steel pipe can withstand:
Continuous service up to approximately 870°C (intermittent)
Good performance in low-temperature environments due to high toughness
9️⃣ How is the quality of ASTM A312 TP304 pipes verified?
Quality control typically includes:
Chemical composition analysis
Tensile and flattening tests
Hydrostatic pressure testing
Ultrasonic testing (UT)
Radiographic testing (RT)
Surface inspection
Heat numbers are marked for full material traceability.
🔟 How do I choose a reliable ASTM A312 TP304 pipe manufacturer?
When selecting a supplier, consider:
Compliance with ASTM A312 standard
Complete inspection documentation
Dimensional tolerance control
Export experience
Stable raw material sourcing
On-time delivery capability
A professional manufacturer should provide both technical support and global shipping solutions.
