Stainless Steel 904L Round Bars Supplier & Exporter | ASTM A479 / UNS N08904
Certified Manufacturer & Supplier | ASTM A479 / ASME SA479 | UNS N08904 | DIN 1.4539 | Round, Hex, Flat & Square Bars
Stainless steel 904L round bars (UNS N08904, ASTM A479) are a high-alloy austenitic grade engineered for superior resistance to sulfuric and phosphoric acid environments — well beyond what standard 316L can withstand. The elevated chromium, nickel, molybdenum, and copper content forms a stable chromium-oxide passive layer, protecting against pitting and crevice corrosion even in high-chloride, high-temperature process streams.
Because 904L contains less carbon than standard austenitic grades, it resists sensitization during welding, making it a preferred choice for pressure vessels, heat exchangers, and pulp & paper digesters that require both weldability and long-term corrosion performance. Unifit Fastener supplies 904L round bars from 3mm to 800mm diameter in hot-rolled, cold-drawn, and centreless-ground finishes.
904L is sometimes specified by its DIN designation 1.4539, or referred to as "super austenitic" stainless steel due to its enhanced alloying content relative to standard 300-series grades. Unifit Fastener stocks 904L round, hex, flat, and rectangular bar sections, distributed to fabricators across India and internationally.
Request QuoteStainless Steel 904L Round Bar Specification
Alloy Name: Stainless Steel 904L | UNS Number: N08904 | DIN Number: 1.4539 | ASTM Standard: A479 | ASME Standard: SA479 | Werkstoff Nr.: 1.4539
The specifications below outline size, grade, and finish details that determine the right 904L bar for your application.
| Category | Specification |
|---|---|
| Standard | ASTM A479, ASTM A479, AMS 5513, AMS 5511, AMS 5647 |
| Dimensions | EN, DIN, JIS, ASTM, BS, ASME, AISI |
| Round Bar Size | Diameter: 3–800mm |
| Hex Bar Size | 2–100mm A/F |
| Flat Bar Size | Thickness: 2–100mm; Width: 10 to 500mm |
| Square Bar Size | 4 to 100mm |
| Angle Bar Size | 3mm×20mm×20mm–12mm×100mm×100mm |
| Rectangular Bars Section | 3.0 to 12.0mm thickness |
| Channel Bar Size | 80×40mm to 150×75mm section; 5.0 to 6.0mm thickness |
| Hollow Bar Size | 32mm OD × 16mm ID to 250mm OD × 200mm ID |
| Billet Size | 1/2 to 495mm Diameter |
| Rectangular Size | 33×30mm to 295×1066mm |
| Hex Bars Finish | Cold drawn, centreless ground, hot rolled, smooth turned, peeled, slit rolled edge, hot rolled annealed, rough turned, bright, polish, grinding, centreless ground & black |
| Hollow Bar Tolerance | H8, H9, H10, H11, H12, H13K9, K10, K11, K12 |
| T-Bar Surface | Bright, Hot Rolled Pickled, Cold Drawn, Sand Blasting Finished, Polished, Hairline |
| Flat Bars Condition | Hardened & tempered, annealed |
| Cold Rolled Bar Technique | Hot Rolled, Cold Drawn, Cold Rolled, Forged Round Bar, Rod |
| Rod Processing | Bar cutting to 650mm |
| Rounds Bar Form | Round, Rod, T-Bar, Channel Bar, Precision Ground Bar, Flat Bar, Square, Blocks, Round Rod, Rings, Hollow, Triangle, Rectangle, Hex (A/F), Threaded, Half Round Bar, Profiles, Billet, Ingot, I/H Bar, Forging etc. |
Types of Stainless Steel 904L Round Bars & Rods
SS 904L is available in multiple bar forms to suit different fabrication needs — from precision-ground round bar for machined components to hexagon and rectangular sections for structural and fastener applications.
SS 904L ROUND BAR
- Stainless Steel 904L Round Bar
- Stainless Steel 904L Square Bars
- SS 904L Polish Round Bar
- SS 904L Cold Drawn Bars
- Stainless Steel 904L Hexagonal Bar
- 904L Stainless Steel Forged Bars
- Stainless Steel 904L Threaded Bar
SS 904L ROUND BAR
- 904L Stainless Steel Hollow Bars
- 904L Stainless Steel Black Bar
- 904L Stainless Steel Bright Round Bar
- Stainless Steel 904L Hexagon Bar
- Stainless Steel 904L Rods
- SS 904L Forged Round Bar
- Stainless Steel 904L Half-Round Bar
SS 904L ROUND BAR
- Stainless Steel 904L Triangle Bar
- Stainless Steel 904L Rectangular Bar
- Stainless Steel 904L Bright Bars
- ASTM A479 904L Stainless Steel Round Bars
- ASME SA 479 904L Stainless Steel Round Bars
- SS 904L Bars
- 904L Stainless Steel Rods
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Chemical Composition of Stainless Steel 904L Round Bars
SS 904L's corrosion performance comes from its high chromium, nickel, and molybdenum content combined with a low carbon ceiling. The table below lists the composition limits per ASTM A479 / UNS N08904.
| Grade | C | Mn | Si | P | S | Cr | Mo | Ni | Cu |
|---|---|---|---|---|---|---|---|---|---|
| SS 904L | 0.020 max | 2.00 max | 1.00 max | 0.040 max | 0.030 max | 19.00 – 23.00 | 4.00 – 5.00 max | 23.00 – 28.00 | 1.00 – 2.00 |
Mechanical Properties of Stainless Steel 904L Round Bars
904L combines high tensile strength with excellent ductility and heat resistance, giving it strong performance across demanding industrial environments. The values below represent typical mechanical properties for annealed bar stock.
| Density | Melting Point | Tensile Strength | Yield Strength (0.2%Offset) | Elongation |
|---|---|---|---|---|
| 7.95 g/cm3 | 1350 °C (2460 °F) | Psi – 71000 , MPa – 490 | Psi – 32000 , MPa – 220 | 35 % |
Stainless Steel 904L Round Bar Size Range
904L round bar is stocked in standard mill lengths from 2000mm to 6000mm, with custom cutting available on request. The table below lists commonly stocked diameters, though intermediate sizes and larger diameters up to 800mm are available on inquiry.
| Diameter (mm) | Diameter (mm) |
|---|---|
| 5.0 mm | 45.0 mm |
| 6.0 mm | 50.0 mm |
| 7.0 mm | 55.0 mm |
| 8.0 mm | 60.0 mm |
| 9.0 mm | 65.0 mm |
| 10.0 mm | 70.0 mm |
| 12.0 mm | 75.0 mm |
| 16.0 mm | 80.0 mm |
| 20.0 mm | 90.0 mm |
| 25.0 mm | 100.0 mm |
| 30.0 mm | 130.0 mm |
| 35.0 mm | 160.0 mm |
| 40.0 mm | 200.0 mm |
ISO Tolerance Chart for SS 904L Round Bars
Dimensional tolerance for SS 904L round bar is classified under standard ISO h (minus), j (plus/minus), and k (plus) grades, ensuring accurate sizing for engineering and machining applications. Reference the appropriate class and diameter range below when specifying tolerance on your purchase order.
| Over | Inc | H7 J7 K7 |
H8 J8 K8 |
H9 J9 K9 |
H10 J10 K10 |
H11 J11 K11 |
H12 J12 K12 |
H13 J13 K13 |
|---|---|---|---|---|---|---|---|---|
1mm |
3mm |
0.009 |
0.014 |
0.025 |
0.040 |
0.06 |
0.09 |
0.14 |
3 |
6 |
0.012 |
0.018 |
0.030 |
0.048 |
0.07 |
0.12 |
0.18 |
6 |
10 |
0.015 |
0.022 |
0.036 |
0.058 |
0.09 |
0.15 |
0.22 |
10 |
18 |
0.018 |
0.027 |
0.043 |
0.070 |
0.11 |
0.18 |
0.27 |
18 |
30 |
0.021 |
0.033 |
0.052 |
0.084 |
0.13 |
0.21 |
0.33 |
30 |
50 |
0.025 |
0.039 |
0.062 |
0.100 |
0.16 |
0.25 |
0.39 |
50 |
80 |
0.030 |
0.046 |
0.074 |
0.120 |
0.19 |
0.30 |
0.46 |
80 |
120 |
0.035 |
0.054 |
0.087 |
0.140 |
0.22 |
0.35 |
0.54 |
120 |
180 |
0.063 |
0.100 |
0.160 |
0.25 |
0.40 |
0.63 |
|
180 |
250 |
0.185 |
0.29 |
0.46 |
0.72 |
|||
250 |
315 |
0.32 |
0.52 |
0.81 |
||||
315 |
400 |
0.36 |
0.57 |
0.89 |
||||
400 |
500 |
0.40 |
0.63 |
0.97 |
||||
500 |
0.44 |
0.70 |
1.10 |
International Standards Cross-Reference for SS 904L
SS 904L round bars supplied by Unifit Fastener are manufactured to be cross-compatible with the major international standards referenced on procurement drawings worldwide:
| Standard of SS 904L | Country / Organization |
|---|---|
| ASTM A479 / A276 | USA (ASTM International) |
| ASME SA479 | USA (ASME) |
| DIN 1.4539 | Germany |
| EN 10088-3 | Europe |
| JIS SUS890L | Japan |
Standard Mill Lengths of SS 904L Round Bars
SS 904L round bar is available in the following standard length bands by diameter, with custom cutting available for fabrication-ready delivery:
| Diameter (mm) | Standard Lengths (m) | Notes |
|---|---|---|
| 3 – 10 | 3, 4, 6 | Small diameter bars for precision components |
| 11 – 50 | 3, 4, 6 | Most commonly used industrial sizes |
| 51 – 100 | 3, 4, 6 | Medium-sized bars for structural applications |
| 101 – 200 | 3, 4, 6 | Large diameter bars; custom lengths available |
| 201 – 800 | Custom lengths | Extra-large bars for heavy-duty industrial applications |
Surface Finish Options for SS 904L Round Bars
SS 904L is available in the same finish range used across our stainless and nickel-alloy bar stock, so fabricators can specify surface condition consistently across mixed-material orders:
| Abbreviation | Finish Type | Abbreviation | Finish Type |
|---|---|---|---|
| P | Polished | HRAP | Hot Rolled Annealed-Pickled |
| CD | Cold Drawn | CF | Cold Finished |
| HF | Hot Finished | PR | Peeled-Reeled |
| CG | Centreless Ground | ST | Smooth Turned |
| SRE | Slit Rolled Edge | RT | Rough Turned |
| BD | Bright Drawn | P&T | Peeled-Turned |
Stainless Steel 904L Round Bars & Rods — Applications
| Industry | Typical Use Case | Why SS 904L |
|---|---|---|
| Petrochemical & Fertilizer Plants | Reactors, heat exchangers | Superior resistance to sulfuric and phosphoric acid at elevated temperatures |
| Pulp & Paper | Digester liquor piping | Low carbon content resists sensitization during welding |
| Offshore & Marine | Oil tower components, valves | High chloride pitting resistance in saline environments |
| Power Generation (Nuclear/Hydro/Thermal) | Pressure vessels, structural components | High mechanical strength with proven long-term corrosion performance |
| Civil & Heavy Engineering | Structural round bars, fasteners | Durability and low maintenance in demanding structural applications |
Stainless Steel 904L Round Bars — Manufactured & Supplied by Unifit Fastener
Unifit Fastener has supplied stainless steel 904L round bars to petrochemical, fertilizer, and pulp & paper fabricators in India and internationally for over a decade. Custom cutting, centreless grinding, and full ASTM A479 / ASME SA479 material certification are available on every order — talk to our technical team to confirm the right finish and tolerance for your application.
FAQ’s About Stainless Steel 904L Round Bars
What is 904L stainless steel?
904L is a high-alloy austenitic stainless steel (UNS N08904, ASTM A479) containing extra chromium, nickel, molybdenum, and copper compared to standard 316L. This gives it superior resistance to sulfuric and phosphoric acid, making it a step up from 316L for aggressive chemical environments.
What are Stainless Steel 904L Round Bars?
SS 904L round bars are cylindrical bar stock manufactured to ASTM B164/ASME SB164 standards, supplied in hot-rolled, cold-drawn, or centreless-ground finishes and available in diameters from 3mm to 800mm for machining into shafts, fasteners, and process equipment components.
Where are Stainless Steel 904L Round Bars commonly used?
904L round bars are commonly used in petrochemical reactors, fertilizer plant piping, pulp and paper digesters, flue-gas desulfurization systems, and offshore/marine components where standard 316L stainless would corrode too quickly.
Are SS 904L Round Bars suitable for pressure vessel applications?
Yes — 904L is widely approved for pressure vessel construction under ASME Section VIII, thanks to its combination of high mechanical strength, low carbon content (reducing weld sensitization risk), and excellent corrosion resistance in acidic process environments.