ASTM A270 Welded Stainless Steel Sanitary Tubing

Metalsin Tech supplies welded stainless steel sanitary tubes made in accordance with ASTM A270. These tubes are usually made from a variety of austenitic, or ferritic/austenitic duplex stainless steel grades. The welded stainless steel sanitary tubing shall be made using an automated welding process with no addition of filler metal during the welding process. These tubes are intended for use in the dairy, food and pharmaceutical industry and having special surface finishes. ASTM A270 sanitary tubes are furnished in sizes up to and including 12 inch [304.8 mm] in outside diameter.

The application of welded stainless steel tubing in food industry.

Our welded stainless steel sanitary tubing undergoes seamless treatment for the weld seam, ensuring no shadowing and a consistently smooth surface. Precision polishing is achieved throughout the process using Chiba wheels, resulting in an internal Ra value of less than 0.2μm—meeting even the most stringent internal surface requirements. The tubing is welded with full nitrogen protection and annealed under pure hydrogen to maintain the highest weld and pipe strength. Test results show tensile strength exceeding 690 MPa, with an expansion rate of over 30%. The tubing performs exceptionally well in fabrication processes like flaring, bending, tube expansion, reduction, curling, and flattening, with no weld seam cracking. Additionally, the tubing has been tested in a 1,000-hour salt spray test, showing no surface corrosion, demonstrating excellent resistance to harsh environments.

Chemical Composition Requirements

Workshop glimpse: the TIG welding production lines for stainless steel sanitary tubes.

Depending on the specific application, the welded stainless steel sanitary tubing may be made from a series of austenitic or ferritic/austenitic duplex stainless steels, typically including TP304, TP304L, TP316, TP316L, S31254, S31803, S32205, or S32750. Their chemical composition are presented in below tables:

Surface Finishes

The surface finish of welded stainless steel sanitary tubing is essential for maintaining hygiene, cleanability, and corrosion resistance, particularly in industries like food processing, pharmaceuticals, and biotechnology. The surface finish is measured by Ra (roughness average), which is the arithmetic average surface roughness normally reported in microinches or microns. A smooth surface with a low Ra value minimizes bacterial growth, ensures easy cleaning, and prevents product contamination. It also enhances corrosion resistance by eliminating surface imperfections and contributes to the overall mechanical performance by reducing stress concentrations. Additionally, a polished finish improves the aesthetic appeal of visible tubing in modern processing plants, making it both functional and visually attractive. According to ASTM A270, the stainless steel sanitary tubing shall be furnished with either mill finish, mechanically polished or electropolished surface finish. The mechanically polished surface finish includes Finish No. 80, No. 120, No. 180, and No. 240. When electropolishing is applied, a bright reflective finish will be produced.