Material Selection8–10 min read
304 vs 316L Stainless Steel: Corrosion, Welding and Cost
Compare the environment and fabrication route before paying for a stainless upgrade.
Author: Mat Grades Editorial DeskRead Guide →
321 Stainless Steel
Primary Designation:TYPE 321
Mat Grades internal verification confirms source-backed fidelity and data integrity. It does not constitute external certification or guaranteed lot conformity. Read engineering disclaimer →
Data Completeness:8 composition elements and 9 condition-specific property values cataloged.
Omitted fields represent unverified properties. "Missing is better than invented."
Key Engineering Properties
Representative source rows, qualified by their reported conditions. Inspect the tables below for all values, limits, and source notes.
Density
7.9 g/cm³TYPICAL · temperature not stated
Thermal Conductivity
16.1 W/(m·K)TYPICAL · at 100 °C
Composition Excerpt
C ≤ 0.08 wt%Carbon (max)
Standard Elemental Basis: MAXTensile Strength
≥ 515 MPaMINIMUM · Annealed · temperature not stated
Engineering Summary
321 Stainless Steel. Source-scoped engineering data is shown with its reported limits and conditions. Unreported properties are not inferred.
Recognized Aliases
Source-backed commercial trade name and short designations cataloged in canonical data.
321 Stainless Steel Specifications & Designations
Standard Designations & Applicable Specifications — Semantically classified designations distinguishing primary standard identifiers, commercial trade names, and applicable specification references.
Direct Standard DesignationsDIRECT DESIGNATION
1 Primary IdentifierScroll horizontally for full designation data
| System | Identifier | Standard System Name | Classification Notes & Provenance |
|---|---|---|---|
| TYPEPRIMARY | 321 | Producer-referenced stainless type | —Ref: Practical Data for Metallurgists, 19th edition |
Applicable Specifications & Product Form ReferencesSPECIFICATION REFERENCE
1 Applicable StandardsScroll horizontally for full standard specifications
| Standards Body | Specification Code | Specification Title / Scope | Relationship Type |
|---|---|---|---|
| 321 | 321 Stainless Steel Engineering Datasheet | Applicable specification reference. | Specification Reference |
Engineering Notice: Applicable specifications establish manufacturing requirements, dimensional tolerances, and test criteria for specific product forms (e.g. bus bar, wire, plate, pipe). They represent applicable technical standards, not alternative or equivalent alloy grades.
321 Stainless Steel Chemical Composition
Chemical Composition (Weight %) — Elemental limits and values from the cited source. Preserves exact semantic limits (minimums, maximums, and ranges).
Scroll horizontally for full elemental limits
| Element | Symbol | Atomic No. | Semantic Basis | Specified Value | Unit | Metallurgical Notes & Qualification | Data Status |
|---|---|---|---|---|---|---|---|
| Carbon | C | 6 | MAXIMUM | ≤ 0.08 | wt% | Source cell: .08max. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Manganese | Mn | 25 | MAXIMUM | ≤ 2.00 | wt% | Source cell: 2.00max. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Silicon | Si | 14 | MAXIMUM | ≤ 1.00 | wt% | Source cell: 1.00max. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Phosphorus | P | 15 | MAXIMUM | ≤ 0.04 | wt% | Source cell: .045max. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Sulfur | S | 16 | MAXIMUM | ≤ 0.03 | wt% | Source cell: .030max. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Chromium | Cr | 24 | RANGE | 17.00 – 19.00 | wt% | Source cell: 17.00/19.00. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Nickel | Ni | 28 | RANGE | 9.00 – 12.00 | wt% | Source cell: 9.00/12.00. Scope: p23, Type 321.Ref: Metallus | VERIFIED |
| Titanium | Ti | 22 | MAXIMUM | ≥ 5 × (C); ≤ 0.6 | wt% | Source requires Ti at least 5 × C and at most 0.60 wt%; the carbon-dependent minimum is not evaluated at the carbon maximum.Ref: Metallus | VERIFIED |
* Elemental percentages are expressed in weight percent (wt%). Values represent applicable specification limits. Unspecified trace elements are not fabricated or assumed.Preserves exact semantic basis
Property Display UnitsSwitch between Canonical SI and Source / US Customary units:
321 Stainless Steel Physical Properties
Source-specific physical properties. Test temperatures are shown only where reported.
Scroll horizontally for full property parameters
| Property Parameter | Canonical SI Value | Semantic Basis | Test Temperature / Context Range | Source Raw Reference | Source Reference | Status |
|---|---|---|---|---|---|---|
| Density | 7.9 g/cm³ | TYPICAL | 7.90 g/cm3 | ATI (Allegheny Technologies Incorporated) | VERIFIED | |
| Elastic Modulus | 193 GPa | TYPICAL | 193 GPa | ATI (Allegheny Technologies Incorporated) | VERIFIED |
321 Stainless Steel Thermal & Thermodynamic Properties
Phase change temperatures, thermal conductivity, specific heat, mean coefficients of thermal expansion across standardized temperature ranges, and recommended thermal processing windows.
Scroll horizontally for full property parameters
| Property Parameter | Canonical SI Value | Semantic Basis | Test Temperature / Context Range | Source Raw Reference | Source Reference | Status |
|---|---|---|---|---|---|---|
| Coefficient of Thermal Expansion | 16.6 µm/(m·K) | TYPICAL | Test Temp: 100 °C | 16.6 10^-6/K | ATI (Allegheny Technologies Incorporated) | VERIFIED |
| Thermal Conductivity | 16.1 W/(m·K) | TYPICAL | Test Temp: 100 °C | 16.1 W/(m·K) | ATI (Allegheny Technologies Incorporated) | VERIFIED |
321 Stainless Steel Electrical Properties
Electrical conductivity and resistivity in their reported units and conditions.
Scroll horizontally for full property parameters
| Property Parameter | Canonical SI Value | Semantic Basis | Test Temperature / Context Range | Source Raw Reference | Source Reference | Status |
|---|---|---|---|---|---|---|
| Electrical Resistivity | 720 nΩ·m | TYPICAL | 72 µΩ·cm | ATI (Allegheny Technologies Incorporated) | VERIFIED |
321 Stainless Steel Mechanical Properties
Contextual Mechanical Properties & Tempers: Engineering strength, ductility, and hardness values grouped by product form, temper, and section thickness. Mechanical properties are contextual and not isotropic averages.
Showing 4 of 4 conditions
Scroll horizontally for all conditions & tempers
| Product Form | Temper / Condition | Section Size | Tensile (UTS) | Yield Strength | Elongation | Shear Strength | Fatigue Strength | Hardness (Scales Preserved) | Status |
|---|---|---|---|---|---|---|---|---|---|
| Plate, Sheet and Strip | Annealed · AnnealedSource values and qualifiersUltimate Tensile Strength: ≥ 515 MPa (MINIMUM)ASTM A240ATI (Allegheny Technologies Incorporated) — ATI 321 Datasheet, Mechanical Properties Table | — | ≥ 515 MPa | — | — | — | — | — | VERIFIED |
| Plate, Sheet and Strip | Annealed · AnnealedSource values and qualifiersYield Strength: ≥ 205 MPa (MINIMUM)ASTM A240 (0.2% offset)ATI (Allegheny Technologies Incorporated) — ATI 321 Datasheet, Mechanical Properties Table | — | — | ≥ 205 MPa | — | — | — | — | VERIFIED |
| Plate, Sheet and Strip | Annealed · AnnealedSource values and qualifiersElongation at Break: ≥ 40 % (MINIMUM)ASTM A240ATI (Allegheny Technologies Incorporated) — ATI 321 Datasheet, Mechanical Properties Table | — · in 50 mm (2 in) | — | — | ≥ 40 % | — | — | — | VERIFIED |
| Plate, Sheet and Strip | AnnealedSource values and qualifiersHRB Hardness: ≤ 95 HRB (MAXIMUM)ATI (Allegheny Technologies Incorporated) — ATI 321 Datasheet, Mechanical Properties Table | — | — | — | — | — | — | ≤ 95 HRB | VERIFIED |
Hardness Integrity Notice: Rockwell B (HRB), Rockwell F (HRF), and Superficial 30T (HR30T) scales are reported on their measured scales without cross-scale mathematical conversion.
Source: See fact-level citations
Practical Engineering & Fabrication Notes
By Mat Grades Editorial Desk · Updated 2026-11-14. Use alongside the specified product standard and supplier certificate.
Machining & shop-floor behavior
For 321 Stainless Steel, a qualified cutting-speed or tool-life recommendation is not supplied in the available record. A relevant hardness example is HRB Hardness: maximum 95 HRB (maximum; Annealed, Plate, Sheet and Strip). Use that supplied condition for a trial of the difficult feature. Record tool changes, burr removal, unclamped dimensions and accepted parts per hour. Relative machinability ratings from different reference scales should not be compared as if they were one common test.
Weldability, brazing & joining
No qualified weld procedure, filler selection or preheat/interpass schedule is established by this material record. Obtain a procedure for the actual joint, supplied condition and section rather than copying one from a nearby grade. The first cataloged strength example is Ultimate Tensile Strength: minimum 515 MPa (minimum; Annealed, Plate, Sheet and Strip). Assess the final part after joining or thermal processing. Include distortion, cleanup and inspection in the quotation. A material designation or favorable process rating is a starting point for qualification, not evidence that an untested joint meets the drawing.
Corrosion & service environment
Assess chlorides, deposits, crevices, temperature and the final cleaned surface together. Stainless is not a promise of immunity to corrosion. Check weld heat tint and embedded iron where fabrication is involved, and do not turn a thermal-property test temperature into a service ceiling. The recorded thermal example is Coefficient of Thermal Expansion: 16.6 µm/(m·K) (typical; ; test temperature 100 °C). State the exposure and inspection access in the design record so that a change of installation or cleaning method triggers a review. The selected composition entries are C maximum 0.08 wt%, Mn maximum 2 wt%, Si maximum 1 wt%. Chemistry documents identity; it does not establish fluid compatibility.
Selection trade-offs & applications
Use TYPE 321, SPECIFICATION 321 Stainless Steel Engineering Datasheet to identify the candidate, then specify the product form and delivered condition separately. A specific component application is not asserted where the source record does not provide one. The listed forms include Plate, Sheet and Strip; confirm the actual stock offered by the supplier. Compare the complete route through machining, joining, finish and inspection. Keep the certificate, required test location and acceptance criteria with the first-article record. A later change of grade, condition or source should be assessed against that same requirement.
Technical references: ATI (Allegheny Technologies Incorporated); Metallus
Austenitic Steel Alloy Family
Corrosion-resistant stainless steels in the Austenitic metallurgical branch sharing equivalent matrix structures.
321Current Grade
321 Stainless Steel
Related Engineering & Metallurgy Guides
Contextual technical guides explaining degradation mechanisms, testing methodologies, and selection criteria relevant to 321 Stainless Steel.
Corrosion & Surface Engineering16 min read
How to Polish Stainless Steel: Methods, Scratch Removal, Finishes & Grain Direction
Stainless steel owes its corrosion resistance to a microscopic, self-healing chromium oxide (Cr₂O₃) passive film. Polishing stainless steel is not merely cosmetic cleaning—it is a controlled mechanical abrasion process requiring strict adherence to grain direction, progressive abrasive refinement, and rigorous cross-contamination control to preserve surface integrity and corrosion performance.
Author: Mat Grades Editorial DeskRead Guide →
Sources
Sources & Provenance Trail: Authoritative reference publications, standards specifications, and data registers cited across this material record.
MetallusPractical Data for Metallurgists, 19th edition
PRIMARY PRODUCER
Reviewed factual transcription; source document SHA-256 is recorded in the capture metadata. No cross-standard equivalence is asserted.
ATI (Allegheny Technologies Incorporated)ATI Technical Data Sheets: Stainless Steel Engineering Specifications
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering datasheet.
Issuing Body: ATI (Allegheny Technologies Incorporated)Revision: Technical Datasheet Series Rev 2024View Source Record ↗
ATI (Allegheny Technologies Incorporated)ATI Technical Data Sheets: Stainless Steel Engineering Specifications
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering datasheet.
Issuing Body: ATI (Allegheny Technologies Incorporated)Revision: Technical Datasheet Series Rev 2024View Source Record ↗
ATI (Allegheny Technologies Incorporated)ATI Technical Data Sheets: Stainless Steel Engineering Specifications
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering datasheet.
Issuing Body: ATI (Allegheny Technologies Incorporated)Revision: Technical Datasheet Series Rev 2024View Source Record ↗
ATI (Allegheny Technologies Incorporated)ATI Technical Data Sheets: Stainless Steel Engineering Specifications
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering datasheet.
Issuing Body: ATI (Allegheny Technologies Incorporated)Revision: Technical Datasheet Series Rev 2024View Source Record ↗
ATI (Allegheny Technologies Incorporated)ATI Technical Data Sheets: Stainless Steel Engineering Specifications
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering datasheet.
Issuing Body: ATI (Allegheny Technologies Incorporated)Revision: Technical Datasheet Series Rev 2024View Source Record ↗
Intellectual Property & Provenance Notice: Mat Grades cites technical literature from recognized industry associations and standards organizations. Underlying technical standards and publication data remain the intellectual property of their respective issuing organizations.