904L (N08904) | BYBOLT

What is 904L and its applications?

904L (UNS N08904) is a high-alloy austenitic stainless steel containing nickel, chromium, molybdenum and copper. It is used in chemical and refinery equipment where standard austenitic stainless grades may have insufficient corrosion resistance.

Chemical and petrochemical plant: Flanges, valves and compatible process equipment.
Refinery systems: Components requiring corrosion review under the actual service conditions.
Water and pulp equipment: Heat-transfer and process components exposed to chloride-containing fluids.

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Engineering Application & Selection Guide

Its alloying improves resistance to relevant acidic and chloride-containing environments. Do not infer higher yield strength simply from its alloy content; mechanical comparisons need matched product forms, conditions and specifications.

904L hex bolts — For acid-processing connections, state the solution-annealed condition and finished-part load requirements.
904L stud bolts — For heat-exchanger flanges, provide the complete chemical composition and operating temperatures.
904L socket head cap screws — For valve-control screws, evaluate electrical contact, process wetting and crevices in the assembled joint.

Use the 904L and 316L comparison alongside process-specific corrosion data. The temperature, acid concentration and oxidizing impurities can change the outcome. A higher-alloy material does not resolve an unsuitable joint geometry.

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904L Composition

Composition limits · wt.%

ElementWeight %

Cr: 19–23%
Ni: 23–28%
Mo: 4–5%
Cu: 1–2%
N: ≤0.10%
C: ≤0.02%
Mn: ≤2.0%
P: ≤0.045%
S: ≤0.035%
Si: ≤1.0%

ASTM / ASME specifications by product form

Finished-product requirements

Specify the finished-fastener mechanical requirements, condition and inspection separately from the starting-stock specification.

904L hex bolt requirements ↗

Fasteners · dimensional references

Product	Reference
Hex bolts	ISO 4014 / ISO 4017 · ASME B18.2.1
Threaded studs	DIN 976-1 · ASME B18.31.2
Hex nuts	ISO 4032 · ASME B18.2.2
Socket head screws	ISO 4762 · ASME B18.3
Flat washers	ISO 7089 / ISO 7090 · ASME B18.21.1
Custom fasteners	Customer drawing

Raw-material specifications

Product form / scope	Reference
Bar & shapes · Specify grade, condition and order requirements.	ASTM A276
Plate, sheet & strip	ASTM A240 / ASME SB625

Dimensions do not define material or finished-part compliance. Specify the grade, condition and applicable requirements.

How to specify round bar, plate, wire and strip ↗

904L Mechanical Properties

Reference sample and condition

Data basis: Catalogue reference minimums
Gauge length: A5, as labelled in supplied table

Key properties	Value
Tensile strength	≥490 MPa
0.2% yield strength	≥220 MPa
Elongation	≥35%

Supplied technical reference · Scanned PDF page 2 · printed page 14

Procurement and application guide

Specify the material and final condition

Evaluate the specific acid and temperature; resistance is environment-dependent.

Material forms in the technical reference: Bar · Shapes · Plate · Sheet · Strip.

Define the finished-part acceptance

Include the material or bolting specification, required final condition, dimensions and quantity. State the service medium, temperature and loading where known. Agree the required tests, inspection coverage and acceptance criteria for the finished part.

Start with the information you have

Send a drawing or share the product form and dimensions. Identify any undecided requirements for review rather than copying a typical property value into the purchase order.

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