321 (S32100) | BYBOLT

What is 321 stainless steel and its applications?

321 stainless steel (UNS S32100) is a titanium-stabilized austenitic grade used in equipment exposed to heat. It is selected where resistance to sensitization matters, including heated process components and thermal-system fabrications.

Thermal equipment: Fabricated components exposed to repeated heating.
Process piping: Equipment requiring a stabilized austenitic material.
Hot-service assemblies: Parts whose selection includes creep and corrosion after thermal exposure.

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Engineering Application & Selection Guide

Titanium binds carbon, reducing chromium-carbide formation at grain boundaries under suitable processing conditions. This mechanism addresses intergranular-corrosion susceptibility; it does not eliminate chloride stress-corrosion cracking.

321 stud bolts — For heated connections, define the required condition and the long-term load rather than relying on a stabilization claim alone.
321 hex bolts — For thermally cycled brackets, include movement of the surrounding structure and the tightening condition.
321 custom fasteners — For fabricated threaded parts, identify welds and thermal processing so their effect on the final condition can be reviewed.

Compare 347 for a niobium-stabilized alternative and 304L when the concern is welding rather than prolonged thermal exposure. Standard 321 and 321H are separate material descriptions; do not assume the H-grade requirements from the family name.

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321 Composition

Selected composition limits · wt.%

ElementWeight %

Cr: 17–19%
Ni: 9–12%
Ti: 5×(C+N)–0.70%
C: ≤0.08%

ASTM / ASME specifications by product form

Finished-product requirements

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

321 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
Plate, sheet & strip · Specify grade, condition and order requirements.	ASTM A240 / ASME SA-240

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 ↗

321 Mechanical Properties

Reference sample and condition

Data basis: Minimums quoted by producer
Test sample form: Sheet test samples
Condition: Annealed
Test temperature: Room temperature
Heat treatment: 1093°C (2000°F), air cooled.
Gauge length: 2 in (50.8 mm)

Key properties	Value
Tensile strength	≥515 MPa
0.2% yield strength	≥205 MPa
Elongation	≥40%

ATI · 321 / 347 · Technical Data Sheet · composition and room-temperature mechanical table ↗

Procurement and application guide

Specify the material and final condition

Match stabilization and heat treatment to the thermal exposure.

Material forms in the technical reference: 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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