Stainless Steel 904L (UNS N08904): Round Bars, Seamless Tubes & Plates — Technical Data Sheet

Quick Answer: What Is Stainless Steel 904L?

Stainless Steel 904L (UNS N08904 / W.Nr. 1.4539) is a premier high-alloy austenitic stainless steel formulated for service environments demanding high mechanical strength and exceptional corrosion resistance. Its high performance stems from the solid-solution strengthening from high nickel (23–28%), molybdenum (4.0–5.0%), and copper (1.0–2.0%) within its stable austenitic chromium-nickel-molybdenum-copper matrix. It is supplied in the solution-annealed condition; no precipitation hardening is involved. Operating efficiently from cryogenic temperatures up to approximately 400°C (750°F) for general service and 870°C (1600°F) for oxidation resistance, Stainless Steel 904L is widely utilized in sulfuric and phosphoric acid plants, seawater heat exchangers, and high-chloride chemical processing.

Product Overview

At the atomic level, its face-centered cubic (FCC) austenitic matrix providing excellent toughness and ductility. Its primary advantage is far superior resistance to sulfuric and phosphoric acids compared with 316L, with a PREN of approximately 35 for seawater service, which yields copper and high molybdenum provide exceptional resistance to reducing acids, while high chromium and nickel resist oxidation and chloride attack.

Shanghai Hangbo Alloy Group Co., Ltd., established in 2012, stands as a top-tier global manufacturer and supplier of Stainless Steel 904L. Operating under a certified ISO 9001:2015 quality management system, we command an export network covering 50+ countries. Our portfolio contains high-precision centerless ground round bars, heavy industrial plates, and high-pressure seamless tubing engineered for critical industrial applications. By managing carbon distribution and grain refinement during melting and forging, we ensure our material provides robust structural performance under severe stress. Every order comes with 100% material traceability and certified documentation, ensuring compliance with strict global engineering standards.

Executive Standards

Shanghai Hangbo Alloy Group Co., Ltd. manufactures Stainless Steel 904L in strict compliance with international technical specifications:

Note: Shanghai Hangbo executes 100% confirmation of chemical compliance using Optical Emission Spectroscopy (OES) for every melt lot.

Chemical Composition

The corrosion-resistant profile of Stainless Steel 904L depends on its exact chemical balance. Chromium ensures high-temperature oxidation resistance, while molybdenum safeguards against localized pitting in chloride environments.

Mechanical Properties

Stainless Steel 904L delivers excellent design allowable stresses. The data below outlines typical properties for annealed stock.

Room-Temperature Mechanical Properties

High-Temperature Performance: Strength Retention Analysis

Stainless Steel 904L retains remarkable mechanical properties under thermal stress, establishing its credentials as a critical superalloy:

How Stainless Steel 904L Is Produced

Round Bar & Forging

• 1. Electric Arc + AOD / VOD Refining: precise control of C, S, and P.
• 2. Hot Forging / Rolling: worked to refine grain structure.
• 3. Solution Annealing: 1050–1150°C followed by rapid cooling.
• 4. Precision Grinding: bars ground to h8/h9 tolerances.

Seamless Tube & Pipe

• 1. Billet Piercing & Extrusion: hollows produced from forged rounds.
• 2. Cold Drawing / Pilgering: precise wall-thickness control.
• 3. Solution Annealing: rapid cooling to retain single-phase austenite.
• 4. Defect Testing: hydrostatic and Eddy Current testing per ASTM standards.

Sheet, Plate & Strip

• 1. Hot Rolling: controlled reduction.
• 2. Cold Rolling: ±0.05 mm gauge control.
• 3. Solution Annealing: rapid quench.
• 4. Pickling: nitric-hydrofluoric bath restores passive surface.

Industry Applications: Solving Engineering Challenges

Chemical Processing

904L is the standard for sulfuric and phosphoric acid plants, acid storage tanks, and heat exchangers handling aggressive reducing acids.

Marine & Seawater

Its high PREN makes it suitable for seawater-cooled heat exchangers, condensers, and desalination equipment.

Pharmaceutical

Used for high-purity process lines and equipment exposed to corrosive cleaning agents.

Pulp & Paper

Handles aggressive bleaching chemicals and acidic process streams.

Quality Assurance: 7-Stage Zero-Defect Inspection Protocol

Shanghai Hangbo Alloy Group Co., Ltd. deploys an intensive inspection matrix to support a zero-defect mandate across all production lines:

• 1. Chemical verification: OES analysis on every melt batch alongside handheld PMI validation on finished products ensures composition parameters match executive limits.
• 2. Ultrasonic Testing (UT): Performed per ASTM A388 standards across all bars and plates to confirm the absence of inner voids, seams, or gas inclusions.
• 3. Eddy Current Testing (ET): Applied 100% to tubes following ASTM E309 protocols to check surface and sub-surface continuity.
• 4. Hydrostatic Pressure Verification: Tubes undergo hydrostatic tests up to 10,000 PSI to verify wall integrity under high-pressure parameters.
• 5. Mechanical Destructive Testing: Tensile, offset yield, elongation, and Brinell hardness examinations are executed per heat lot to verify strength criteria.
• 6. Dimensional Metrology Check: Digital calipers and computerized laser sensors measure geometry, guaranteeing all diameter, wall, and length tolerances match orders.
• 7. Visual and Microstructure Audit: Surface quality checks are paired with metallographic microscope tests to evaluate grain size (ASTM E112) and phase homogeneity.

All items leave our facilities accompanied by ISO 9001:2015 certification and EN 10204 3.1 Mill Test Certificates. Third-party inspection options through SGS, TUV, or Bureau Veritas (BV) are organized upon customer request.

Frequently asked questions