ASTM A270 TP304 Seamless Sanitary Stainless Steel Tube with External Thread End

ASTM A270 TP304 Sanitary Stainless Steel Tube is manufactured from TP304 austenitic stainless steel for sanitary piping and tubing systems requiring controlled surface finish, cleanability and corrosion resistance.

The product is available as seamless sanitary tubing and can be supplied with machined external thread ends according to customer drawings or specified thread standards. The threaded end is an additional end-processing configuration and should be specified separately from the ASTM A270 material and tubing requirements.

ASTM A270/A270M covers seamless, welded and heavily cold-worked welded austenitic and ferritic/austenitic stainless steel sanitary tubing. The standard is intended for sanitary tubing used in applications such as dairy and food processing, with pharmaceutical-quality requirements available as supplementary requirements. The current ASTM A270/A270M-24 scope covers tubing up to 12 in. [300 mm] outside diameter.

For sanitary applications, surface finish and internal cleanliness are important selection parameters. ASTM A270 provides various surface-finish options, including mechanically polished and electropolished finishes, as well as specified maximum roughness requirements.

Product Specifications

Material: TP304 Stainless Steel

Mechanical Properties

External Thread End

The tube can be supplied with a machined external thread at one or both ends.

The thread configuration can be manufactured according to:

• Customer drawing
• Purchase order
• NPT
• BSPT
• BSPP
• Metric thread
• Other specified thread standards

Tube Surface Finish

Surface finish is an important part of sanitary tubing selection.

Available finishes can include:

Mill Finish

Suitable for applications where the project specification does not require a polished sanitary surface.

Mechanical Polishing

The outside surface, inside surface or both can be polished according to the required finish.

Electropolishing

Electropolished tubing can be supplied when the project requires a higher-grade sanitary surface.

Specified Surface Roughness

Maximum surface roughness can be specified according to the applicable order requirement.

ASTM A270 identifies several surface finishes, including mill finish, mechanically polished finishes, No. 80, No. 120, No. 180 and No. 240 finishes, electropolished finish and maximum roughness average requirements.

Manufacturing Process

The typical manufacturing process for seamless TP304 sanitary tubing includes:

1. Stainless steel billet inspection
2. Heat number identification
3. Hot piercing
4. Tube rolling / sizing
5. Cold drawing where required
6. Solution annealing
7. Straightening
8. Cutting
9. Surface treatment
10. End machining
11. External thread machining
12. Dimensional inspection
13. Surface inspection
14. NDT / hydrostatic testing
15. Cleaning
16. Marking
17. Packaging

For seamless tubing, the manufacturing route does not involve welding at any stage. ASTM A270 distinguishes seamless tubing from welded and heavily cold-worked welded tubing.

Dimensional Control

Dimensional inspection can cover:

• Outside diameter
• Wall thickness
• Ovality
• Length
• Straightness
• Thread outside diameter
• Thread pitch
• Thread length
• Thread profile
• End squareness

For threaded products, the thread dimensions should be checked against the specified thread standard or approved customer drawing.

Quality Control

Chemical Analysis

Each heat can be checked for:

• Carbon
• Manganese
• Silicon
• Phosphorus
• Sulfur
• Chromium
• Nickel

Mechanical Testing

Testing can include:

• Tensile test
• Yield strength
• Elongation
• Hardness

Tube Testing

Depending on the applicable order and ASTM requirements:

• Hydrostatic test
• Eddy current test
• Other nondestructive electric testing

ASTM A270 requires each tube to undergo applicable mechanical or testing procedures, including reverse flattening, hydrostatic testing or nondestructive electric testing.

Surface Inspection

Inspection can verify:

• Surface condition
• Polishing quality
• Internal surface condition
• External surface condition
• Thread condition
• Surface roughness where specified