UNS S30403 seamless pipe is a low carbon version of the standard 304 austenitic stainless steel, designed for applications requiring enhanced resistance to intergranular corrosion after welding or elevated temperature exposure. The "UNS S30403" designation corresponds to the Unified Numbering System for metals, identifying a composition of 18-20% chromium and 8-12% nickel, with a maximum carbon content of 0.030%.

The low carbon content is the defining characteristic of UNS S30403. Standard 304 (UNS S30400) contains up to 0.080% carbon, which can lead to sensitization – the precipitation of chromium carbides at grain boundaries during welding or high-temperature service. This sensitization depletes chromium adjacent to the grain boundaries, making the material susceptible to intergranular corrosion (weld decay). UNS S30403's 0.030% maximum carbon content virtually eliminates this risk, allowing the material to be used in welded assemblies without post-weld heat treatment.

The low carbon content distinguishes UNS S30403 from standard S30400.

EN 1.4307 (X2CrNi18-9) Chemical Composition:

UNS S30403 seamless pipe delivers the following mechanical properties in the solution annealed condition:

High-Temperature Mechanical Properties (Typical for 304L):

Low-Temperature Impact Properties:

UNS S30403 maintains excellent toughness down to cryogenic temperatures, making it suitable for low-temperature and cryogenic service.

The seamless manufacturing process for UNS S30403 pipe ensures consistent quality.

Step 1 – Billet Preparation
Solid round billets of UNS S30403 composition are inspected, cut to length, and heated.

Step 2 – Rotary Piercing
The heated billet is pierced to form a hollow shell.

Step 3 – Elongation and Rolling
The hollow shell is elongated and rolled to achieve target dimensions.

Step 4 – Sizing and Reducing
The pipe is sized to precise outer diameter and straightened.

Step 5 – Cold Drawing (optional)
For tighter tolerances and better surface finish, cold drawing through a die and over a mandrel is employed.

Step 6 – Solution Annealing
The pipe is heated to 1010-1120°C (1850-2050°F) and then water quenched to dissolve carbides and restore corrosion resistance.

Step 7 – Pickling or Bright Annealing
Scale is removed through acid pickling, or the pipe is bright annealed in a controlled atmosphere.

Step 8 – Straightening, Cutting, and Finishing
The pipe is straightened, cut to length, and ends prepared.

UNS S30403 seamless pipe is used across a wide range of industries where corrosion resistance requirements are moderate and cost is a factor.

• Process piping for dilute acids and alkalis

• Heat exchanger tubes for non-corrosive or mildly corrosive media

• Tanks and vessel interconnecting piping

• Solvent and reagent transfer lines

• Steam and condensate return lines

The low carbon content allows welding without post-weld heat treatment, essential for field-fabricated systems.

• Dairy processing (milk, cream, yogurt)

• Beverage handling (beer, wine, juice, soft drinks)

• Food product transfer (soups, sauces, edible oils)

• CIP (Clean-in-Place) systems

• Food preparation and packaging equipment

• Purified water systems

• Clean steam distribution

• API transfer lines (non-corrosive formulations)

• Fermentation and bioreactor support systems

• Freshwater and potable water distribution

• Wastewater treatment plant piping

• Aeration and sludge handling lines

• Irrigation systems

• Paper machine shower lines

• Dilute chemical handling

• Condensate return systems

• Compressed air systems

• Hydraulic and pneumatic tubing

• Instrumentation and control lines

• Structural and support tubing

• Heat exchangers (mild service)

• Handrails and guardrails

• Structural supports and frames

• Decorative tubing for building interiors

• Furniture frames

UNS S30403 offers good corrosion resistance in mildly corrosive environments.

When to upgrade to 316L (UNS S31603):

• Coastal or marine environments

• Higher chloride levels (>100 ppm)

• Stagnant seawater exposure

• Higher temperature chloride service

• Sulfuric or phosphoric acid service above dilute concentrations

• Pitting or crevice corrosion concerns

For inquiries, technical data sheets, or a quotation for UNS S30403 seamless pipe (TP304L seamless pipe / 1.4307 seamless pipe / low carbon 304 seamless tube), please contact our sales team.