SS6934 304L Stainless Steel Nipple

304L Stainless Steel Nipples Description

304L stainless steel nipples are manufactured from an austenitic alloy with a low carbon content to prevent sensitisation during welding. The carbon content of ≤0.03% prevents the precipitation of chromium carbide in heat‐affected zones, thereby maintaining corrosion resistance in welded assemblies. Annealed and pickled surfaces (Ra ≤0.8 μm) provide effective passivation, whilst 18–20% chromium forms a self-repairing oxide layer to deliver pitting resistance in chloride‐containing environments. With a tensile strength of ≥485 MPa and an elongation of ≥40%, these nipples withstand thermal cyclic stresses from cryogenic (–200°C) to elevated temperatures (425°C). Electropolishing options improve cleanability for hygienic applications.

304L Stainless Steel Nipples Applications

• Chemical processing: Corrosion‐resistant fluid transfer lines, reactor penetrations
• Pharmaceuticals: USP Class VI‐compliant pipes for bioprocessing
• Maritime: Seawater cooling systems and deck fittings
• Food & Beverage: CIP/SIP system connections, fermentation tank couplings
• Semiconductors: High‐purity gas and chemical supply lines

304L Stainless Steel Nipples Packaging

Our products are packaged in customer‐specific cartons of various sizes determined by the material dimensions. Small items are securely packed in PP cartons, whereas larger items are placed in custom‐made wooden crates. We ensure strict adherence to packaging modifications and utilise suitable cushioning materials to guarantee optimal protection during transport.

Packaging: Carton, wooden crate, or customer‐specific.

Please refer to the Packaging Details for further information.

Manufacturing Process

Testing Procedures

(1) Chemical composition analysis – Techniques such as GDMS or XRF verify compliance with purity requirements.

(2) Mechanical properties testing – This includes tensile strength, yield strength and elongation tests to assess material performance.

(3) Dimensional inspection – Measurements of thickness, width and length verify adherence to specified tolerances.

(4) Surface quality inspection – Visual and ultrasonic tests check for defects such as scratches, cracks or inclusions.

(5) Hardness testing – Determination of material hardness confirms uniformity and mechanical reliability.

Please refer to the SAM Testing Procedures for detailed information.

FAQs on 304L Stainless Steel Nipples

Q1. How corrosion-resistant is 304L stainless steel in seawater or marine environments?

The low carbon content of 304L (≤0.03%) prevents chromium depletion at the grain boundaries, thereby maintaining a consistent chromium oxide passivation layer in chloride-rich seawater. It is not as corrosion-resistant as 316L; however, regularly flushing with fresh water and avoiding prolonged immersion in stagnant seawater ensure long-term performance. For full immersion in seawater, 316L should be considered; for splash zones or occasional exposure, 304L is sufficient.

Q2. Can 304L nipples be safely welded to other stainless steel grades without affecting corrosion resistance?

Yes, provided that welding procedures with low heat input (e.g. TIG) are used and overheating is avoided to preclude carbide precipitation. Cleaning after welding with a stainless steel brush or pickling paste removes discoloration and restores the passive layer. A suitable welding addition ensures compatibility; however, welding to 316L may present a minimal galvanic risk in aggressive environments.

Q3. How can I remove surface rust or stains from 304L nipples without damaging the material?

Gently scrub with a soft nylon brush and a mild acidic cleaning agent (e.g. citric acid or vinegar solution). Do not use abrasive sponges or harsh chemicals such as bleach that may scratch or etch the surface. For stubborn stains, use a specialised stainless steel polish or passivation gel to restore the oxide layer without altering dimensions. Rinse the surface thoroughly after cleaning.

Additional Information

Common Preparation Methods

304L nipples are vacuum-induction melted (VIM) to control sulphur/phosphorous impurities, hot forged at 1 150–1 260°C and subsequently solution annealed at 1 040–1 120°C, followed by rapid water quenching to dissolve carbides. The nipples are precision turned to a tolerance of ±0.05 mm and then pickled in an HNO₃/HF bath to remove scale. For medical grades, electropolishing in phosphoric-sulphuric acid achieves a surface finish of Ra ≤0.4 μm. Final passivation is carried out in accordance with ASTM A967 Method 2 to ensure the integrity of the chromium oxide layer. Batch traceability includes PMI verification using XRF and intergranular corrosion tests in accordance with ASTM A262 Practice E.