AISI 321 stainless steel (UNS S32100, EN 1.4541) 321

spore: profile
id: stainless-321
spore_version: 0.2
family: stainless-austenitic
name: AISI 321 stainless steel (UNS S32100, EN 1.4541)
abbreviation: '321'
role: titanium-stabilised austenitic stainless steel for high-temperature and welded service
category: metals
type: steels-and-stainless
summary: |
  AISI 321 (UNS S32100, EN 1.4541) is an austenitic stainless steel with 17 to 19 % chromium and 9 to 12 % nickel, stabilised with titanium. Its datasheets give a density of 7.92 g/cm3 and an elastic modulus of 193 GPa, and a mean thermal expansion of 16.6 ppm/K from 20 to 100 degC. Sheet to ASTM A240 has a minimum 0.2 % proof stress of 205 MPa and a minimum tensile strength of 515 MPa. The titanium keeps the carbon tied up, so the steel resists carbide precipitation in the 800 to 1500 degF (427 to 815 degC) range, which is the reason for the grade.
best_for: 'Welded parts that run hot in oxidising air, from 427 to 850 degC: titanium holds the grade against carbide precipitation in the 800 to 1500 degF range'
weakest_at: Strength when annealed (about 241 MPa typical yield) and cold-work strength only, plus exposure of 900 to 1500 degF for long periods, which lowers general corrosion resistance
identity:
  formula: Fe balance, with Cr 17.0 to 19.0 wt %, Ni 9.0 to 12.0 wt %, C max 0.08 wt %, Mn max 2.00 wt %, Si max 0.75 wt %, N max 0.10 wt % and Ti 5x(C+N) to 0.70 wt % (ATI 321 composition table)
  source: ati-321
  where: Composition table, Minimum and Maximum (wt %) columns, rows Cr, Ni, C, Ti and Fe
  designations:
    - system: UNS
      code: S32100
      source: upmet-321
      where: Header line, AMS 5510 / AMS 5645 / UNS S32100
    - system: EN
      code: '1.4541'
      source: righton-321
      where: Specifications block, Commercial 321, EN 1.4541
    - system: EN name
      code: X6CrNiTi18-10
      source: righton-321
      where: Alloy designations list, first bullet
    - system: AISI
      code: '321'
      source: righton-321
      where: Alloy designations list, AISI 321
    - system: ASTM
      code: A240
      note: plate, sheet and strip
      source: ati-321
      where: Specifications line, ASTM A240 / ASME SA-240
    - system: AMS
      code: '5510'
      note: sheet, strip and plate
      source: ati-321
      where: Specifications line, AMS 5510
    - system: AMS
      code: '5645'
      note: bar, wire and forging
      source: upmet-321
      where: Header line, AMS 5510 / AMS 5645 / UNS S32100
    - system: BS
      code: 321S31
      source: aircraftmaterials-ams5510
      where: Specifications list, BS 970 321S31
    - system: BS
      code: 321 S51
      source: swiss-4541
      where: 'Relevant current and obsolete standards list, BS : 321 S51'
    - system: AFNOR
      code: Z6CNT 18-10
      source: swiss-4541
      where: 'Relevant current and obsolete standards list, AFNOR : Z6CNT 18-10'
    - system: Trade name
      code: ATI 321
      source: ati-321
      where: Page title, ATI 321 Austenitic Stainless Steel (UNS S32100)
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - propulsion-and-tanks
    - heat-shields
properties:
  - benchmark: density
    label: Density, 321 (United Performance Metals datasheet)
    value: 7.92
    unit: g/cm3
    scope: material
    conditions:
      grade: '321'
      temperature: not stated
      unit_in_source: 0.286 lb/in3
    method: Value printed in a supplier datasheet table of physical properties
    status: ground
    source: upmet-321
    where: Physical Properties of 321 table, Density g/cm3 column, grade 321 row
  - benchmark: density
    label: Density, UNS S32100 at 20 °C (Combined Metals datasheet)
    value: 8.09
    unit: g/cm3
    scope: material
    conditions:
      grade: UNS S32100
      temperature: 20 °C
      unit_in_source: 0.29 lb/in3 at 70 °F
    method: Value printed in a distributor datasheet; the page says the figures come mainly from third-party melting mills and are for reference only
    status: ground
    note: The other datasheet figure, 7.92 g/cm3, is 0.17 g/cm3 lower; both are kept because the sources do not state their test basis in the same way.
    source: combmet-321
    where: Physical Properties table, Density row, At 20°C column
  - benchmark: melting_point
    label: Melting range, 321
    value: 1398
    value_high: 1446
    bound: range
    unit: °C
    scope: material
    conditions:
      grade: '321'
      unit_in_source: 2550 to 2635 °F
      form: not stated
    method: Range printed in a supplier datasheet table of physical properties
    status: ground
    source: upmet-321
    where: Physical Properties of 321 table, Melting Range °C column
  - benchmark: elastic_modulus
    label: Modulus of elasticity in tension, 321
    value: 193
    unit: GPa
    scope: material
    conditions:
      grade: '321'
      temperature: not stated
      unit_in_source: 28 x 10^6 psi
    method: Value printed in a supplier datasheet table of physical properties
    status: ground
    source: upmet-321
    where: Physical Properties of 321 table, Modulus of Elasticity in Tension GPa column
  - benchmark: cte
    label: Mean coefficient of linear thermal expansion, 20 to 100 °C
    value: 16.6
    unit: ppm/K
    scope: material
    conditions:
      grade: '321'
      temperature: 20 to 100 °C
      unit_in_source: 16.6 x 10-6 cm/cm/°C; 9.2 x 10-6 in/in/°F
    method: Mean coefficient printed in a supplier datasheet table
    status: ground
    source: upmet-321
    where: Mean Coefficient of Linear Thermal Expansion table, row 20-100 °C
  - benchmark: cte
    label: Mean coefficient of linear thermal expansion, 20 to 1000 °C
    value: 20.5
    unit: ppm/K
    scope: material
    conditions:
      grade: '321'
      temperature: 20 to 1000 °C
      unit_in_source: 20.5 x 10-6 cm/cm/°C; 11.4 x 10-6 in/in/°F
    method: Mean coefficient printed in a supplier datasheet table
    status: ground
    source: upmet-321
    where: Mean Coefficient of Linear Thermal Expansion table, row 20-1000 °C
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 321, 20 to 100 °C
    value: 16.3
    unit: W/(m·K)
    scope: material
    conditions:
      grade: '321'
      temperature: 20 to 100 °C
      unit_in_source: 112.5 Btu·in/(hr·ft2·°F)
    method: Value printed in a supplier datasheet table of physical properties
    status: ground
    source: upmet-321
    where: Thermal Conductivity table, row 20-100 °C, W/m·K column
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 321, 20 to 500 °C
    value: 21.4
    unit: W/(m·K)
    scope: material
    conditions:
      grade: '321'
      temperature: 20 to 500 °C
      unit_in_source: 147.7 Btu·in/(hr·ft2·°F)
    method: Value printed in a supplier datasheet table of physical properties
    status: ground
    source: upmet-321
    where: Thermal Conductivity table, row 20-500 °C, W/m·K column
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 1.4541 at 20 °C (Swiss Steel Group datasheet)
    value: 15
    unit: W/(m·K)
    scope: material
    conditions:
      grade: '1.4541'
      temperature: 20 °C
      unit_in_source: W/m K
    method: Value printed in a manufacturer datasheet, Physical Properties block
    status: ground
    note: Lower than the 16.3 W/(m·K) of the 20 to 100 °C range in the other datasheet; the two use different temperature bases.
    source: swiss-4541
    where: Physical Properties block, thermal conductivity at 20°C (W/m K) row
  - benchmark: specific_heat
    label: Specific heat capacity, 321, 0 to 100 °C
    value: 500
    unit: J/kg K
    scope: material
    conditions:
      grade: '321'
      temperature: 0 to 100 °C
      unit_in_source: 0.12 Btu/lb·°F, 32 to 212 °F
    method: Value printed in a supplier datasheet table of physical properties
    status: ground
    source: upmet-321
    where: Specific Heat table, row 0-100 °C, J/kg K column
  - benchmark: electrical_resistivity
    label: Electrical resistivity, 321 at 20 °C
    value: 72
    unit: microhm·cm
    scope: material
    conditions:
      grade: '321'
      temperature: 20 °C
      unit_in_source: microhm·cm
    method: Value printed in a supplier datasheet table of physical properties
    status: ground
    note: The same table gives 78 microhm·cm at 100 °C and 126 microhm·cm at 900 °C.
    source: upmet-321
    where: Electrical Resistivity table, row 20 °C, microhm·cm column
  - benchmark: yield_strength
    label: Yield strength, 0.2 % proof, sheet (ASTM A240 minimum)
    value: 205
    bound: lower
    unit: MPa
    scope: material
    conditions:
      form: sheet
      specification: ASTM A240
      measure: 0.2 % proof stress
      temper: not printed
      unit_in_source: 205 Min MPa
    method: Minimum value printed in a distributor datasheet, sheet row of the ASTM A240 table
    status: ground
    source: righton-321
    where: Mechanical properties, ASTM A240 Sheet table, row Proof Stress
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, sheet (ASTM A240 minimum)
    value: 515
    bound: lower
    unit: MPa
    scope: material
    conditions:
      form: sheet
      specification: ASTM A240
      temper: not printed
      unit_in_source: 515 Min MPa
    method: Minimum value printed in a distributor datasheet, sheet row of the ASTM A240 table
    status: ground
    source: righton-321
    where: Mechanical properties, ASTM A240 Sheet table, row Tensile Strength
  - benchmark: elongation
    label: Elongation A50 mm, sheet (ASTM A240 minimum)
    value: 35
    bound: lower
    unit: '%'
    scope: material
    conditions:
      form: sheet
      specification: ASTM A240
      gauge_length: A50 mm
      unit_in_source: 35 Min %
    method: Minimum value printed in a distributor datasheet, sheet row of the ASTM A240 table
    status: ground
    source: righton-321
    where: Mechanical properties, ASTM A240 Sheet table, row Elongation A50 mm
  - benchmark: yield_strength
    label: Yield strength, annealed, typical
    value: 241
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      basis: typical, based on ASTM A240
      unit_in_source: 35 ksi
    method: Typical value printed in a distributor datasheet, Typical Room Temperature Mechanical Properties table
    status: ground
    note: Typical, not a minimum. A specification minimum of 205 MPa is recorded separately for sheet.
    source: combmet-321
    where: Typical Room Temperature Mechanical Properties table, row Annealed, 0.2% Offset Yield column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, annealed, typical
    value: 586
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      basis: typical, based on ASTM A240
      unit_in_source: 85 ksi
    method: Typical value printed in a distributor datasheet
    status: ground
    source: combmet-321
    where: Typical Room Temperature Mechanical Properties table, row Annealed, Tensile Strength (UTS) column
  - benchmark: elongation
    label: Elongation in 2 in, annealed, typical
    value: 55
    unit: '%'
    scope: material
    conditions:
      temper: annealed
      gauge_length: 2 in (50.8 mm)
      basis: typical, based on ASTM A240
    method: Typical value printed in a distributor datasheet
    status: ground
    source: combmet-321
    where: Typical Room Temperature Mechanical Properties table, row Annealed, Elongation in 2 in column
  - benchmark: yield_strength
    label: Rp0.2 yield, solution annealed, typical (Swiss Steel Group)
    value: 320
    unit: N/mm2
    scope: material
    conditions:
      temper: solution annealed
      basis: typical
      specification_minimum_as_printed: 190 N/mm2 (EN 10088-3)
    method: Typical value printed in a manufacturer datasheet, mechanical properties table
    status: ground
    note: This typical value is well above the 205 MPa minimum in the ASTM A240 sheet table. The two are different product forms and standards, so they are not averaged.
    source: swiss-4541
    where: Heat treatment / mechanical properties table, row yield strength, Typical column
  - benchmark: max_service_temp
    label: Maximum continuous service temperature in oxidising atmosphere
    value: 850
    unit: °C
    scope: material
    conditions:
      exposure: continuous, oxidising atmosphere
      sulphur_bearing_atmosphere: 750 °C (printed separately)
    method: Maximum temperature printed in a manufacturer datasheet for continuous exposure
    status: ground
    source: swiss-4541
    where: Resistance to high temperature exposure section, first two bullets
  - benchmark: hardness_brinell
    label: Hardness, Brinell maximum, bar
    value: 217
    bound: upper
    unit: HB
    scope: material
    conditions:
      form: bar
      unit_in_source: 217 max HB
    method: Maximum value printed in a distributor datasheet, Bar table
    status: ground
    note: hardness_brinell is not a canonical name in spores/property-canon.yaml; see gaps.
    source: righton-321
    where: Mechanical properties, Bar table, row Hardness Brinell
corrosion:
  - environment: Natural waters (rural and industrial)
    headline: Excellent resistance in most natural waters, provided chloride, salt and hydrochloric or organic acid levels are low.
    effect: The Swiss Steel Group datasheet says 1.4541 shows excellent resistance to corrosion in most natural waters, rural and industrial, provided the chloride, salt and concentrations of hydrochloric and organic acids are low. It also says the grade stays resistant to intergranular corrosion after welding.
    rating: low
    conditions:
      basis: qualitative statement, no test result or rate given
    source: swiss-4541
    where: Corrosion resistance section, first paragraph
  - environment: Carbide precipitation range, 800 to 1500 °F (427 to 815 °C)
    headline: Titanium stabilises the grade against chromium carbide precipitation in the 800 to 1500 °F range.
    effect: The titanium addition reduces or prevents carbide precipitation during welding and in 800 to 1500 °F service, according to the NKS datasheet. Long-time exposure in the 900 to 1500 °F range may lower its general corrosion resistance, but the grade still shows better intergranular corrosion resistance than unstabilised grades.
    rating: moderate
    conditions:
      exposure: long-time, 900 to 1500 °F
      basis: datasheet statement, no rate given
    source: nks-321
    where: Description paragraph and Corrosion paragraph
  - environment: Oxidising air at high temperature
    headline: The grade has good oxidation resistance and is rated for continuous service up to 850 °C in oxidising atmospheres.
    effect: The Combined Metals datasheet says the grade has excellent resistance to oxidation and intergranular corrosion. The Swiss Steel Group datasheet gives continuous exposure limits of 850 °C in oxidising atmospheres and 750 °C in oxidising atmospheres that contain sulphur.
    rating: low
    conditions:
      basis: datasheet limits for continuous exposure; no scaling rate given
    source: swiss-4541
    where: Resistance to high temperature exposure section
  - environment: Nitric and sulphur acids
    headline: Good resistance to nitric acid and moderate resistance to sulphur acids.
    effect: The NKS datasheet says Type 321 resists nitric acid well and the sulphur acids moderately, and shows excellent resistance to organic chemicals and a wide range of inorganic chemicals.
    rating: low
    conditions:
      basis: qualitative statement, no concentration or temperature given
    source: nks-321
    where: Corrosion paragraph
risks:
  hazards:
    - text: 'NIST SRM 1171 (AISI 321) safety data sheet: not classified as a physical or health hazard under OSHA 29 CFR 1910.1200, with no pictograms, hazard statements or signal word. The material is an article under 1910.1200(c) and no SDS is required.'
      ghs: []
      source: nist-srm1171
      where: Opening paragraph and Exemption paragraph
  failure_risks:
    - mode: Loss of general corrosion resistance after long exposure at 900 to 1500 °F
      trigger: Long-time service in the 900 to 1500 °F range
      consequence: The NKS datasheet says general corrosion resistance may be lowered, although intergranular corrosion resistance is still better than unstabilised grades. No rate is given.
      severity: moderate
      source: nks-321
      where: Corrosion paragraph
    - mode: Attack in natural waters with high chloride, salt or acid content
      trigger: Waters or acids where chloride, salt, hydrochloric or organic acid concentrations are not low
      consequence: The Swiss Steel Group datasheet gives excellent corrosion resistance only when these are low. It gives no pitting or crevice test result.
      severity: moderate
      source: swiss-4541
      where: Corrosion resistance section, first paragraph
  side_effects: []
  handling:
    - text: Weldable with all processes except gas welding; filler metal Novonit 4316 or 4551 is recommended (Swiss). NKS says AWS E/ER 347 or E/ER 321 filler is most often specified. Maximum inter-pass temperature 200 °C; heat tint must be removed by pickling or mechanical means and the surface passivated.
      source: swiss-4541
      where: Welding section
    - text: Machinability is poor, and titanium carbo-nitrides change the machining behaviour compared with low-carbon grades such as 1.4307 (Swiss Steel Group datasheet).
      source: swiss-4541
      where: Machining section and general properties list
    - text: Solution anneal at 1075 to 1125 °C followed by rapid cooling in air or water for optimum properties (Swiss); NKS gives an annealing range of 1750 to 2050 °F, water quench or air cool.
      source: nks-321
      where: Processing paragraph
  mitigations: []
uses:
  - application: propulsion-and-tanks
    device: Aircraft exhaust stacks and jet engine parts
    example: United Performance Metals lists aircraft exhaust stacks, manifolds and jet engine parts among the industry applications of alloy 321.
    source: upmet-321
    where: Industry Applications list
  - application: structures
    device: Welded pressure vessels and boiler casings
    example: Combined Metals lists welded pressure vessels, boiler casings, firewalls and stack liners among the applications of Type 321.
    source: combmet-321
    where: Description, Applications include paragraph
  - application: heat-shields
    device: Annealing covers and high-temperature tempering equipment
    example: Combined Metals lists annealing covers and high-temperature tempering equipment, for continuous or intermittent service at 800 to 1500 °F (427 to 816 °C).
    source: combmet-321
    where: Description paragraph and Applications include list
supply:
  - subject: Nickel (mine production, 9 to 12 wt % of the grade)
    producers:
      - country: Indonesia
        share_percent: 66.7
        year: 2025
      - country: Philippines
        share_percent: 6.9
        year: 2025
      - country: Russia
        share_percent: 5.1
        year: 2025
      - country: New Caledonia
        share_percent: 3.6
        year: 2025
    critical_lists: []
    recycling: The USGS nickel summary gives US nickel-containing scrap, including stainless-steel scrap, as an import source, but no recycling share for global nickel was read.
    substitutes:
      - 'USGS: low-nickel, duplex or ultrahigh-chromium stainless steels have been substituted for austenitic grades in construction; titanium alloys can substitute for nickel-base alloys in corrosive environments.'
    source: usgs-mcs2026-nickel
    where: World Mine Production and Reserves table, 2025e world total 3,900,000 t; shares calculated by Space Mushroom from the country values 2,600,000 (Indonesia), 270,000 (Philippines), 200,000 (Russia) and 140,000 (New Caledonia); Substitutes paragraph
  - subject: Chromium (mine production, 17 to 19 wt % of the grade)
    producers:
      - country: South Africa
        share_percent: 45.1
        year: 2025
      - country: Turkey
        share_percent: 17.6
        year: 2025
      - country: Kazakhstan
        share_percent: 13.7
        year: 2025
      - country: India
        share_percent: 5.9
        year: 2025
    critical_lists: []
    recycling: 'USGS: recycled chromium, contained in reported stainless-steel scrap receipts, accounted for 21 % of US apparent consumption in 2025.'
    substitutes:
      - 'USGS: chromium has no substitute in stainless steel, the leading end use.'
    source: usgs-mcs2026-chromium
    where: World Mine Production and Reserves table, 2025e world total 51,000 thousand t chromium content; shares calculated by Space Mushroom from the country values 23,000 (South Africa), 9,000 (Turkey), 7,000 (Kazakhstan) and 3,000 (India); Domestic Production and Use and Substitutes paragraphs
documents:
  - title: United Performance Metals, 321 Stainless Steel Datasheet (AMS 5510, AMS 5645, UNS S32100)
    type: datasheet
    url: https://www.upmet.com/sites/default/files/products/datasheet/321-datasheet.pdf
    year: 2026
  - title: Righton Blackburns, Stainless Steel 1.4541 (321) datasheet, updated 05 August 2021
    type: datasheet
    url: https://www.rightonblackburns.co.uk/datasheets/view/Righton-Blackburns-Ltd_Stainless-Steel-14541-321-Bar_462.pdf
    year: 2021
  - title: Combined Metals of Chicago, Alloy 321 Stainless Steel material datasheet (UNS S32100), REV 2022 08 05
    type: datasheet
    url: https://www.combmet.com/wp-content/uploads/2023/02/cmc_321_data_sheet.pdf
    year: 2022
  - title: NKS, 321 Stainless Steel product datasheet
    type: datasheet
    url: https://nks.com/wp-content/uploads/321-Stainless-Steel.pdf
  - title: Swiss Steel Group, Data sheet 1.4541 X6CrNiTi 18-10 (revision 4541-0)
    type: datasheet
    url: https://swisssteel-group.com/content-media/documents/Data-Sheets/Stainless-Steel/w_4541engl.pdf
    year: 2000
  - title: Aircraft Materials, AMS 5510 Stainless Steel 321 page
    type: database
    url: https://aircraftmaterials.com/data/alstst/ams5510.html
  - title: ATI 321 Austenitic Stainless Steel (UNS S32100) product page
    type: datasheet
    url: https://atimaterials.com/Products/ati-321
  - title: NIST SRM 1171 (AISI 321) Material Safety Data Sheet, dated 29 October 2014
    type: sds
    url: https://tsapps.nist.gov/srmext/MSDS/1171-MSDS.pdf
    year: 2014
  - title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
gaps:
  - No outgassing, total mass loss, atomic oxygen erosion, radiation or thermal-cycling data for AISI 321 was found in an opened source, so the space-environment section is empty.
  - Pitting resistance number, critical pitting temperature and stress-corrosion data were not found in the opened sources; the corrosion section is qualitative.
  - Titanium supply (sponge, ferrotitanium) was not read; supply covers nickel and chromium only.
  - Critical-mineral list membership for nickel and chromium was not printed in the USGS 2026 summaries opened for this run, so critical_lists is empty.
  - 'Silicon limit disagrees between sources: AMS 5510 (aircraftmaterials page) prints 0.25 to 1.00 %, while the ATI page prints a maximum of 0.75 %. Neither is entered as a property.'
  - Density, modulus and expansion values differ slightly between the datasheets, and the Swiss Steel Group datasheet gives density as 7.9 kg/dm3 (no temperature). The Swiss value is not entered as a property.
  - The Swiss Steel Group datasheet gives electrical resistivity as 0.73 with the unit printed as W mm2/m, which is not a standard unit form; it is not entered.
  - hardness_brinell is not in spores/property-canon.yaml; it is used as a short name for the Brinell maximum of 217 HB from the Righton bar table.
  - Impact energy (Swiss Steel Group typical 200 J at 25 °C, specification 100 J minimum) and the sheet and plate hardness values from the United Performance Metals table were not entered, to keep one value per property.
  - The ATI page gives sheet and strip density as 0.286 lb/in3 and plate as 0.29 lb/in3 without a g/cm3 value printed on the fetched page; no conversion was made.
  - Chemical resistance to specific organic acids, and the creep and stress-rupture values the NKS and Swiss sources describe as better than 304, were not found as numbers.
  - The Aperam 1.4541 product page prints typical composition values with no unit and was used only for designations, not for numbers.
sources:
  upmet-321:
    title: 321 Stainless Steel Datasheet, United Performance Metals
    id: AMS 5510 / AMS 5645 / UNS S32100 datasheet, text on page 1
    url: https://www.upmet.com/sites/default/files/products/datasheet/321-datasheet.pdf
    year: 2026
    kind: datasheet
    license: Supplier datasheet, cited not reproduced; states the data are for information only
  righton-321:
    title: Righton Blackburns Ltd, Stainless Steel 1.4541 (321) datasheet
    id: Datasheet updated 05 August 2021
    url: https://www.rightonblackburns.co.uk/datasheets/view/Righton-Blackburns-Ltd_Stainless-Steel-14541-321-Bar_462.pdf
    year: 2021
    kind: datasheet
    license: Distributor datasheet, indicative only, cited not reproduced
  combmet-321:
    title: Combined Metals of Chicago, Alloy 321 Stainless Steel material datasheet
    id: UNS S32100, EN DIN 1.4541, REV 2022 08 05
    url: https://www.combmet.com/wp-content/uploads/2023/02/cmc_321_data_sheet.pdf
    year: 2022
    kind: datasheet
    license: Distributor datasheet, reference only, cited not reproduced
  nks-321:
    title: NKS, 321 Stainless Steel datasheet
    id: ASTM A240 product datasheet
    url: https://nks.com/wp-content/uploads/321-Stainless-Steel.pdf
    kind: datasheet
    license: Supplier datasheet, cited not reproduced
  swiss-4541:
    title: Swiss Steel Group, Data sheet 1.4541 X6CrNiTi 18-10
    id: Revision 4541-0, created 21.02.2000
    url: https://swisssteel-group.com/content-media/documents/Data-Sheets/Stainless-Steel/w_4541engl.pdf
    year: 2000
    kind: datasheet
    license: Manufacturer datasheet, cited not reproduced
  aircraftmaterials-ams5510:
    title: Stainless Steel 321 (AMS 5510 / AMS 5645), Aircraft Materials
    id: Specifications list and typical properties table
    url: https://aircraftmaterials.com/data/alstst/ams5510.html
    kind: web
    license: Web reference, cited not reproduced; says specifications are a guideline only
  ati-321:
    title: ATI 321 Austenitic Stainless Steel (UNS S32100), ATI
    id: Product page, plate, sheet and strip
    url: https://atimaterials.com/Products/ati-321
    kind: datasheet
    license: Manufacturer product page, cited not reproduced
  nist-srm1171:
    title: NIST SRM 1171 (AISI 321) Material Safety Data Sheet
    id: Stainless Steel (Cr 17-Ni 11-Ti 0.3), dated 29 October 2014
    url: https://tsapps.nist.gov/srmext/MSDS/1171-MSDS.pdf
    year: 2014
    kind: datasheet
    license: US government document, public domain
  usgs-mcs2026-nickel:
    title: 'Mineral Commodity Summaries 2026: Nickel, USGS'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: US government, public domain
  usgs-mcs2026-chromium:
    title: 'Mineral Commodity Summaries 2026: Chromium, USGS'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
    kind: report
    license: US government, public domain
license: CC-BY-4.0
updated: '2026-10-25'
review:
  status: draft
  method: assistant
  checked_values: 20
  unreachable: 2
  caveats: 4
  note: 'Values read by an AI assistant on 2026-10-25 from the pages and PDFs named in each entry. Unreachable: Aubert and Duval alloy page (404), MakeItFrom (403), Alloys International (403). Caveats: the datasheets disagree on density, thermal conductivity and typical yield; the Swiss Steel Group sheet dates from 2000; the NIST SRM is a single reference material for the grade; supply shares are calculated from USGS tonnages.'
story:
  recipe:
    line: AISI 321 is an iron-based alloy of chromium and nickel, stabilised with titanium so that the carbon is tied up as carbides or carbo-nitrides rather than as chromium carbide at grain boundaries (Swiss Steel Group datasheet). The composition ranges are the ASTM A240 limits printed in the ATI composition table, in weight percent.
    parts:
      - name: Iron
        symbol: Fe
        share: balance, printed as Balance in the ATI composition table
        role: The matrix of the alloy; the other elements are dissolved in it.
      - name: Chromium
        symbol: Cr
        share: 17.0 to 19.0 wt %
        role: Gives the stainless steel its corrosion and oxidation resistance (Swiss and NKS datasheets).
      - name: Nickel
        symbol: Ni
        share: 9.0 to 12.0 wt %
        role: Keeps the structure austenitic; NKS describes the alloy as non-magnetic.
      - name: Titanium
        symbol: Ti
        share: 5x(C+N) minimum to 0.70 wt % maximum
        role: The stabilising element that reduces or prevents carbide precipitation in the 800 to 1500 °F range (NKS datasheet).
      - name: Carbon
        symbol: C
        share: 0.08 wt % maximum
        role: Kept low; titanium binds the carbon that remains.
      - name: Manganese
        symbol: Mn
        share: 2.00 wt % maximum
        role: Minor element, listed as a maximum in the ATI composition table.
      - name: Silicon
        symbol: Si
        share: 0.75 wt % maximum
        role: Minor element, listed as a maximum in the ATI composition table; AMS 5510 lists 0.25 to 1.00 %.
      - name: Nitrogen
        symbol: 'N'
        share: 0.10 wt % maximum
        role: Minor element that also enters the titanium requirement, 5x(C+N).
  risk_groups:
    - title: For people
      lead: The only hazard statement in the sources is the NIST SRM 1171 safety data sheet for AISI 321, which classifies the material as an article.
      level: 1
      verdict: Not classified
      points:
        - label: Solid alloy
          line: The NIST SRM 1171 safety data sheet for AISI 321 is not classified as a physical or health hazard under OSHA and carries no pictogram or signal word.
        - label: Processing
          line: The sources read here cover the solid alloy only. Grinding, cutting and welding fumes were not read from a source in this run.
    - title: If it fails
      lead: 'The failure routes in these sources are qualitative: long exposure at 900 to 1500 °F, and waters or acids with high chloride or acid content.'
      points:
        - label: Long-time heat
          line: The NKS datasheet says long-time exposure at 900 to 1500 °F may lower general corrosion resistance, though the grade still resists intergranular corrosion better than unstabilised grades.
        - label: Chloride and acids
          line: The Swiss Steel Group datasheet gives excellent corrosion resistance only when chloride, salt, hydrochloric and organic acid concentrations are low.
    - title: Handling and storage
      points:
        - label: Welding
          line: Weldable with all processes except gas welding. Filler metal 4316 or 4551 is recommended, and the maximum inter-pass temperature is 200 °C.
        - label: Heat tint
          line: Heat tint from welding must be removed by pickling or mechanical means and the surface passivated, to restore corrosion resistance.
  why: AISI 321 is a titanium-stabilised 18-8 austenitic stainless steel. Its datasheets give a density of 7.92 g/cm3 and an elastic modulus of 193 GPa, and a mean thermal expansion of 16.6 ppm/K from 20 to 100 °C. The titanium addition is the reason to choose it over 304 for welded parts that run in the 800 to 1500 °F range, since it reduces carbide precipitation there.
  uses:
    - where: Hot exhaust and jet parts
      line: United Performance Metals lists aircraft exhaust stacks, manifolds and jet engine parts among the applications of alloy 321.
    - where: Welded pressure equipment
      line: Combined Metals lists welded pressure vessels, boiler casings, firewalls and stack liners. The datasheet says the grade is used for continuous or intermittent service at 800 to 1500 °F (427 to 816 °C).
    - where: Annealing and tempering equipment
      line: Annealing covers and high-temperature tempering equipment are listed as typical applications by Combined Metals and NKS.
  can_do:
    - label: Carry heat
      value: 16.3 W/(m·K)
      benchmark: thermal_conductivity
      line: Thermal conductivity is 16.3 W/(m·K) from 20 to 100 °C and 21.4 W/(m·K) from 20 to 500 °C in the United Performance Metals table.
    - label: Stay in shape when hot
      value: 20.5 ppm/K
      benchmark: cte
      line: The mean coefficient of thermal expansion is 16.6 ppm/K from 20 to 100 °C and 20.5 ppm/K from 20 to 1000 °C.
    - label: Hold load at sheet strength
      value: 205 MPa minimum yield
      benchmark: yield_strength
      line: Sheet to ASTM A240 has a minimum 0.2 % proof stress of 205 MPa and a minimum tensile strength of 515 MPa, with at least 35 % elongation over 50 mm.
    - label: Survive continuous heat
      value: 850 °C
      benchmark: max_service_temp
      line: The Swiss Steel Group datasheet gives 850 °C as the maximum for continuous exposure in oxidising atmospheres, and 750 °C where the atmosphere contains sulphur.
  compare: The datasheets for AISI 321 agree closely on density (7.92 and 8.09 g/cm3 at different stated bases) and on modulus (193 GPa), but they differ on thermal conductivity (15 W/(m·K) at 20 °C from Swiss Steel Group, 16.3 W/(m·K) from 20 to 100 °C from United Performance Metals) and on annealed strength. The values are for the grade as printed in each source and should be read as examples of spread, not a ranking.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Thermal expansion
      benchmark: cte
  handling:
    - Specify the product form and temper, since the sheet minimums and annealed typical values differ.
    - Use the filler metal and inter-pass limit from the welding section of the datasheet.
    - Remove heat tint and passivate after welding.
  good_for:
    - 'Welded hot parts: titanium stabilisation against carbide precipitation in the 800 to 1500 °F range (NKS datasheet).'
    - Continuous service up to 850 °C in oxidising atmospheres (Swiss Steel Group datasheet).
    - Non-magnetic annealed stainless steel with 193 GPa modulus (datasheets).
  watch_out:
    - Long exposure at 900 to 1500 °F can lower general corrosion resistance (NKS datasheet).
    - Chloride and strong acid content must be low for the stated corrosion resistance (Swiss Steel Group datasheet).
    - Machinability is poor compared with low-carbon grades (Swiss Steel Group datasheet).
    - No space-environment data (outgassing, atomic oxygen, radiation) was found for this grade in the sources read.
  verdict: AISI 321 is a titanium-stabilised 18-8 stainless steel for welded parts that run hot. It has a density of 7.92 g/cm3, a modulus of 193 GPa, and a 205 MPa minimum yield in sheet, and it is rated to 850 °C in oxidising air for continuous service. Its weak points are the long exposure at 900 to 1500 °F and the chloride limits, and this profile has no sourced space-environment data.