spore: profile
id: stainless-347
spore_version: 0.2
family: stainless-austenitic
name: AISI 347 stainless steel
abbreviation: '347'
role: Niobium-stabilised austenitic stainless steel for welded, hot service
category: metals
type: steels-and-stainless
summary: |
  AISI 347 (UNS S34700, EN 1.4550) is an austenitic stainless steel with 17 to 19 % chromium and 9 to 13 % nickel, stabilised with niobium (columbium) so that it resists intergranular attack after exposure in the chromium-carbide range of 427 to 816 °C. The UPMET datasheet prints a density of 7.96 g/cm3 for grade 347 and a melting range of 1398 to 1446 °C. The Combmet datasheet gives a modulus of 193 GPa at 20 °C and typical annealed values of 640 MPa tensile strength and 250 MPa yield. The Smith datasheet prints a maximum use temperature in air of 800 °C.
best_for: 'Welded hot-service parts that cannot be re-annealed afterwards: niobium stabilisation resists intergranular attack, and the grade is rated to 800 °C in air'
weakest_at: 'Strength when hot: tensile strength falls from 93.3 ksi at 68 °F to 69.5 ksi at 800 °F (Rolled Alloys), and no vacuum, radiation or atomic-oxygen data were found'
identity:
  formula: 'Fe-based austenitic alloy: Fe balance, Cr 17.00 to 19.00 %, Ni 9.00 to 13.00 % (9.00 to 12.00 % in UPMET and Combmet), C 0.08 % maximum, Mn 2.00 % maximum, S 0.03 % maximum, Nb plus Ta at 10 x C minimum and 1.00 % maximum (ASTM A240 limits)'
  source: aalco347
  where: Chemical composition table, ASTM A240 sheet limits (Aalco datasheet); Nb plus Ta row from the UPMET chemical composition table
  designations:
    - system: UNS
      code: S34700
      source: combmet347
      where: 'Header, UNS: S34700'
    - system: EN
      code: '1.4550'
      source: combmet347
      where: 'Header, EN-DIN: 1.4550'
    - system: EN name
      code: X6CrNiNb18-10
      source: alfa347
      where: Title line and header, X6CrNiNb18-10, 1.4550 EN 10088-2:2014
    - system: AISI
      code: '347'
      source: alfa347
      where: Title line and header, AISI 347
    - system: JIS
      code: SUS347
      source: tachart347
      where: 'Alias heading, JIS: SUS347'
    - system: ASTM
      code: A240
      note: plate, sheet and strip
      source: aalco347
      where: 'Spec line, Spec: ASTM A240'
    - system: ASTM
      code: A269
      note: tube
      source: finetubes347
      where: Designations block, ASTM A269
    - system: ASTM
      code: A312
      note: pipe
      source: finetubes347
      where: Designations block, ASTM A312
    - system: ASTM
      code: TP347
      note: tube and pipe grade
      source: alfa347
      where: Header list, TP347
    - system: AMS
      code: '5512'
      note: sheet, coil and bar
      source: upmet347
      where: Header line, AMS 5512 / AMS 5646 / UNS S34700
    - system: AMS
      code: '5646'
      source: upmet347
      where: Header line, AMS 5512 / AMS 5646 / UNS S34700
    - system: ASME
      code: SA-240
      source: rolled347
      where: 'Specifications block, ASME: SA-240'
    - system: Trade name
      code: Alloy 347
      source: combmet347
      where: Document title, Alloy 347 Stainless Steel
    - system: Trade name
      code: Type 347
      source: rolled347
      where: Product description paragraph, Type 347 stainless steel
tags:
  environments: []
  stresses: []
  applications:
    - thermal-control
    - structures
properties:
  - benchmark: density
    label: Density, grade 347
    value: 7.96
    unit: g/cm3
    scope: material
    conditions:
      grade: '347'
      temperature: not stated in the table
      unit_in_source: 0.288 lb/in3
    method: Value printed in a manufacturer datasheet
    status: ground
    source: upmet347
    where: Physical Properties table, row 347, column Density g/cm3
  - benchmark: melting_point
    label: Melting range, grade 347
    value: 1398
    value_high: 1446
    bound: range
    unit: °C
    scope: material
    conditions:
      grade: '347'
      unit_in_source: 2550-2635 °F
      pressure: not stated
    method: Melting range printed in a manufacturer datasheet
    status: ground
    source: upmet347
    where: Physical Properties table, row 347, column Melting Range °C
  - benchmark: elastic_modulus
    label: Modulus of elasticity in tension, 20 °C
    value: 193
    unit: GPa
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 193 x 10^3 MPa (28.0 x 10^3 ksi at 70 °F)
    method: Value printed in a manufacturer datasheet
    status: ground
    source: combmet347
    where: Physical Properties table, column At 20oC, row Modulus of Elasticity (E)
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 20 °C
    value: 16.3
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 9.5 Btu-in./ft.2 hr.-oF at 70 °F
    method: Value printed in a manufacturer datasheet
    status: ground
    source: combmet347
    where: Physical Properties table, column At 20oC, row Thermal Conductivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 20 to 500 °C
    value: 21.4
    unit: W/(m·K)
    scope: material
    conditions:
      temperature_range: 20 to 500 °C
      unit_in_source: 147.7 Btu-in/hr-ft2-°F
    method: Value printed in a manufacturer datasheet
    status: ground
    note: The UPMET thermal table is not labelled by grade; the datasheet title is for 347 sheet, coil and bar.
    source: upmet347
    where: Thermal Conductivity table, row 20-500 (68-932 °F), column W/m·K
  - benchmark: specific_heat
    label: Specific heat capacity, 0 to 100 °C
    value: 500
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature_range: 0 to 100 °C
      unit_in_source: 0.12 Btu/lb·°F
    method: Value printed in a manufacturer datasheet
    status: ground
    note: The UPMET specific heat table is not labelled by grade; the datasheet title is for 347 sheet, coil and bar.
    source: upmet347
    where: Specific Heat table, row 0-100 (32-212 °F), column J/kg K
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 20 °C
    value: 72
    unit: µΩ·cm
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 28.4 µΩ·in at 70 °F
    method: Value printed in a manufacturer datasheet
    status: ground
    source: combmet347
    where: Physical Properties table, column At 20oC, row Electrical Resistivity
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 900 °C
    value: 126
    unit: µΩ·cm
    scope: material
    conditions:
      temperature: 900 °C
      unit_in_source: microhm·cm
    method: Value printed in a manufacturer datasheet
    status: ground
    note: The UPMET resistivity table is not labelled by grade; the datasheet title is for 347 sheet, coil and bar.
    source: upmet347
    where: Electrical Resistivity table, row 900 (1652 °F), column microhm·cm
  - benchmark: cte
    label: Mean coefficient of linear thermal expansion, 20 to 100 °C
    value: 16.6
    unit: ppm/K
    scope: material
    conditions:
      temperature_range: 20 to 100 °C
      unit_in_source: 16.6 x 10-6 cm/cm/°C (9.2 x 10-6 in/in/°F)
    method: Value printed in a manufacturer datasheet
    status: ground
    source: upmet347
    where: Mean Coefficient of Linear Thermal Expansion table, row 20-100 (68-212 °F), column cm/cm/°C
  - benchmark: cte
    label: Mean coefficient of linear thermal expansion, 20 to 600 °C
    value: 18.9
    unit: ppm/K
    scope: material
    conditions:
      temperature_range: 20 to 600 °C
      unit_in_source: 18.9 x 10-6 cm/cm/°C (10.5 x 10-6 in/in/°F)
    method: Value printed in a manufacturer datasheet
    status: ground
    source: upmet347
    where: Mean Coefficient of Linear Thermal Expansion table, row 20-600 (68-912 °F), column cm/cm/°C
  - benchmark: yield_strength
    label: Yield strength 0.2 % offset, minimum, ASTM A240 sheet
    value: 205
    bound: lower
    unit: MPa
    scope: material
    conditions:
      spec: ASTM A240
      form: sheet
      measure: 0.2 % proof stress, minimum
    method: Minimum value printed in a supplier datasheet quoting ASTM A240
    status: ground
    source: aalco347
    where: Mechanical Properties table, row Proof Stress, value 205 Min MPa
  - benchmark: yield_strength
    label: Yield strength 0.2 % offset, typical, annealed
    value: 250
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      basis: typical values based on ATI source, ASTM A240
      unit_in_source: 37 ksi
    method: Typical value printed in a supplier datasheet
    status: ground
    source: combmet347
    where: Typical Room Temperature Mechanical Properties table, row Annealed, column 0.2% YS
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, minimum, ASTM A240 sheet
    value: 515
    bound: lower
    unit: MPa
    scope: material
    conditions:
      spec: ASTM A240
      form: sheet
    method: Minimum value printed in a supplier datasheet quoting ASTM A240
    status: ground
    source: aalco347
    where: Mechanical Properties table, row Tensile Strength, value 515 Min MPa
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, typical, annealed
    value: 640
    unit: MPa
    scope: material
    conditions:
      temper: annealed
      basis: typical values based on ATI source, ASTM A240
      unit_in_source: 93 ksi
    method: Typical value printed in a supplier datasheet
    status: ground
    source: combmet347
    where: Typical Room Temperature Mechanical Properties table, row Annealed, column Tensile Strength (UTS)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength at 800 °F, typical
    value: 69.5
    unit: ksi
    scope: material
    conditions:
      temperature: 800 °F as printed (about 427 °C)
      basis: typical tensile and impact properties
      form: not stated
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: rolled347
    where: Typical Tensile and Impact Properties table, column 800, row Ultimate Tensile Strength, ksi
  - benchmark: elongation
    label: Elongation, minimum, ASTM A240 sheet
    value: 40
    bound: lower
    unit: '%'
    scope: material
    conditions:
      spec: ASTM A240
      form: sheet
      gauge_length: A50 mm
    method: Minimum value printed in a supplier datasheet quoting ASTM A240
    status: ground
    source: aalco347
    where: Mechanical Properties table, row Elongation A50 mm, value 40 Min %
  - benchmark: elongation
    label: Elongation, typical, annealed
    value: 45
    unit: '%'
    scope: material
    conditions:
      temper: annealed
      gauge_length: 2 in (50.8 mm)
      basis: typical values based on ATI source, ASTM A240
    method: Typical value printed in a supplier datasheet
    status: ground
    source: combmet347
    where: Typical Room Temperature Mechanical Properties table, row Annealed, column Elongation % in 2 in
  - benchmark: hardness
    label: Hardness, maximum, Brinell (plate)
    value: 201
    bound: upper
    unit: HB
    scope: material
    conditions:
      product_form: plate
      scale: Brinell
    method: Maximum value printed in a manufacturer datasheet
    status: ground
    source: upmet347
    where: Mechanical Properties table, row Hardness Max., Brinell (Plate), column Type 347
  - benchmark: hardness
    label: Hardness, maximum, Rockwell B (sheet and strip)
    value: 92
    bound: upper
    unit: HRB
    scope: material
    conditions:
      product_form: sheet and strip
      scale: Rockwell B
    method: Maximum value printed in a manufacturer datasheet
    status: ground
    source: upmet347
    where: Mechanical Properties table, row Hardness Max., RB (Sheet & Strip), column Type 347
  - benchmark: hardness
    label: Hardness, typical, annealed (HRBW)
    value: 84
    unit: HRBW
    scope: material
    conditions:
      temper: annealed
      basis: typical values based on ATI source, ASTM A240
    method: Typical value printed in a supplier datasheet
    status: ground
    source: combmet347
    where: Typical Room Temperature Mechanical Properties table, row Annealed, column Hardness Rockwell
  - benchmark: max_service_temp
    label: Maximum use temperature in air
    value: 800
    unit: °C
    scope: material
    conditions:
      environment: air
      basis: stated as the maximum use temperature, no duration given
    method: Value printed in a manufacturer datasheet
    status: ground
    source: smith347
    where: Physical Properties table, row Maximum use temperature in air
corrosion:
  - environment: Chromium-carbide sensitisation range, 427 to 816 °C (welding and stress relief)
    headline: Niobium stabilisation keeps the grade resistant to intergranular corrosion after exposure in the chromium-carbide range.
    effect: Combmet says the 347 alloys are stabilised by columbium and resist intergranular corrosion after exposure at 800 to 1500 °F (427 to 816 °C). Rolled Alloys says the grade has good resistance to intergranular corrosion in the as-welded condition.
    rating: low
    conditions:
      basis: datasheet statements; no corrosion rate printed
      stabiliser: columbium (niobium)
    source: combmet347
    where: Description paragraph of the Combmet datasheet
  - environment: Polythionic acid in oil refineries
    headline: Type 347 resists polythionic acid stress corrosion cracking, a refinery hazard.
    effect: Rolled Alloys says both 347 and 321 offer good resistance to polythionic acid stress corrosion cracking encountered in oil refineries. Smith says the alloy has good resistance to polythionic acid stress corrosion cracking and is useful around reactor plants.
    rating: low
    conditions:
      basis: datasheet statements; no test duration or concentration printed
    source: rolled347
    where: Opening paragraph and Applications list of the Rolled Alloys datasheet
  - environment: Strongly oxidising service and high-temperature air
    headline: Type 347 has slightly better corrosion resistance than Type 321 in strongly oxidising environments, and is useful to 1500 °F.
    effect: Rolled Alloys says 347 has slightly improved corrosion resistance over type 321 in strongly oxidising environments, and that its high-temperature oxidation resistance is similar to 304 stainless steel. Smith prints a maximum use temperature in air of 800 °C.
    rating: low
    conditions:
      basis: datasheet statements; no oxidation rate printed
    source: rolled347
    where: Opening paragraph of the Rolled Alloys datasheet; Smith Physical Properties table
  - environment: Chloride and general wet service
    headline: Smith describes the grade as having excellent pitting resistance and good resistance to most chemicals.
    effect: The Smith datasheet states excellent pitting resistance and good resistance to most chemicals, without a critical pitting temperature or a chloride limit.
    rating: low
    conditions:
      basis: general statement; no test data printed
    source: smith347
    where: Corrosion resistance box of the Smith datasheet
risks:
  hazards:
    - text: 'Uddeholm safety information sheet for steel articles, nickel entry: H317 May cause an allergic skin reaction. H351 Suspected of causing cancer by inhalation. H372 Causes damage to organs through prolonged or repeated exposure by inhalation. Signal word DANGER. The same sheet says massive steel products need no label, but dust and fumes from grinding, polishing, welding or cutting carry the risk.'
      ghs:
        - H317
        - H351
        - H372
      source: uddeholm-sis
      where: Classification of the major hazard substances, Nickel entry (the sheet is for Uddeholm alloys, not a 347 sheet)
    - text: 'The same sheet quotes the CLP rule for steels: more than 10 % nickel is classed STOT RE1, 1 to 10 % nickel is classed STOT RE2, and more than 1 % nickel is classed Carcinogen Category 2. A 347 specification of 9 to 13 % nickel straddles the 10 % limit, so the class depends on the actual heat.'
      ghs: []
      source: uddeholm-sis
      where: Note under the Nickel entry
    - text: The sheet says alloys containing nickel or chromium may cause health hazards by inhalation of dusts and fumes produced by mechanical and thermal treatment such as grinding, polishing, welding or cutting, and that prolonged or repeated skin contact may cause dermatitis in nickel-sensitised persons.
      ghs: []
      source: uddeholm-sis
      where: Description of Hazards
  failure_risks:
    - mode: Intergranular attack from chromium carbide
      trigger: Exposure in the chromium-carbide range of 427 to 816 °C, for example after welding, where the carbon is not tied up by niobium
      consequence: Chromium carbide forms at grain boundaries and the metal loses intergranular corrosion resistance. Combmet states that the niobium addition is what prevents this.
      severity: moderate
      source: combmet347
      where: Description paragraph of the Combmet datasheet
    - mode: Polythionic acid stress corrosion cracking
      trigger: Polythionic acid formed in oil-refinery equipment
      consequence: Rolled Alloys and Smith say 347 has good resistance to this cracking. The sources print no crack or failure data for the grade.
      severity: moderate
      source: rolled347
      where: Opening paragraph and Applications list of the Rolled Alloys datasheet
    - mode: Loss of strength when hot
      trigger: Service at 800 °F and above
      consequence: Typical tensile strength falls from 93.3 ksi at 68 °F to 69.5 ksi at 800 °F, and typical 0.2 % yield falls from 36.5 ksi to 29.7 ksi over the same range (Rolled Alloys).
      severity: low
      source: rolled347
      where: Typical Tensile and Impact Properties table, columns 68 and 800
  side_effects: []
  handling:
    - text: The grade is chosen where welded parts cannot be annealed afterwards, since Rolled Alloys says it keeps good resistance to intergranular corrosion in the as-welded condition.
      source: rolled347
      where: Features list of the Rolled Alloys datasheet
    - text: Smith says Type 347 is essentially non-magnetic in the annealed condition and can only be hardened by cold working, so strength depends on the temper.
      source: smith347
      where: Description paragraph of the Smith datasheet
    - text: 'Specify the temper and product form: the minimum values of ASTM A240 apply to sheet, and the typical annealed values in the Combmet sheet were measured on the ATI basis.'
      source: combmet347
      where: Typical Room Temperature Mechanical Properties table and its footnote
  mitigations: []
uses:
  - application: thermal-control
    device: Aircraft exhaust stacks and furnace heating elements
    example: UPMET lists aircraft exhaust stacks, aircraft collector rings, cabin heaters, boiler casings and furnace heating elements among industry applications for 347 sheet, coil and bar. The GE GT193 aircraft engine specification is also listed.
    source: upmet347
    where: Industry Applications list
  - application: structures
    device: Hanger rods, fired heater tubes, thermowells and reactor components
    example: Smith lists oil refineries, fired heater tubes, thermowells, fluid catalytic cracking units, hanger rods and reactor components as typical applications for the grade.
    source: smith347
    where: Typical Applications list
  - application: thermal-control
    device: Recuperator tube sheets and fired heater tubes in refineries
    example: Rolled Alloys lists recuperator tube sheets, shells and supports, fired heater tubes and distributor trays, with the note that 347 is especially suited where temperatures exceed 550 °F and sulfidation resistance is needed.
    source: rolled347
    where: Applications list of the Rolled Alloys datasheet
supply:
  - subject: Nickel (world mine production, nickel content, 2025 estimate)
    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
      - country: Canada
        share_percent: 3.6
        year: 2025
    critical_lists: []
    recycling: 'USGS: nickel recovered from scrap accounted for about 60 % of U.S. apparent consumption in 2025; most secondary nickel went into new stainless steel and alloys.'
    substitutes:
      - 'USGS: low-nickel, duplex or ultrahigh-chromium stainless steels have been substituted for austenitic grades in construction; titanium alloys can substitute for nickel or nickel-base alloys in corrosive environments.'
    source: usgs-nickel-2026
    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; 270,000; 200,000; 140,000; 140,000. Recycling; Substitutes; Domestic Production and Use (stainless and alloy steel more than 85 % of U.S. consumption).
  - subject: Chromium (world mine production, chromium content, 2025 estimate)
    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 in stainless-steel scrap receipts accounted for 21 % of U.S. apparent consumption in 2025.'
    substitutes:
      - 'USGS: chromium has no substitute in stainless steel, the leading end use.'
    source: usgs-chromium-2026
    where: World Mine Production and Reserves table, 2025e world total 51,000 thousand t; shares calculated by Space Mushroom from the country values 23,000; 9,000; 7,000; 3,000. Recycling paragraph; Substitutes paragraph.
  - subject: Niobium (columbium) (world mine production, niobium content, 2025 estimate)
    producers:
      - country: Brazil
        share_percent: 92.9
        year: 2025
      - country: Canada
        share_percent: 5.4
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 0.9
        year: 2025
    critical_lists: []
    recycling: 'USGS: scrap recovery of niobium was negligible; niobium was recycled mainly as part of niobium-bearing steels and superalloys.'
    substitutes:
      - 'USGS: ceramic matrix composites, molybdenum, tantalum and tungsten can replace niobium in high-temperature superalloy uses, with a performance loss or higher cost.'
    source: usgs-niobium-2026
    where: World Mine Production and Reserves table, 2025e world total 112,000 t; shares calculated by Space Mushroom from the country values 104,000; 6,000; 970. Brazil is also printed as approximately 93 % of global production in the Domestic Production and Use text. Recycling; Substitutes; Events, Trends, and Issues (steels about 77 % of U.S. consumption).
documents:
  - title: Datasheet for 347 Stainless Steel Sheet, Coil and Bar, AMS 5512, 5646 (United Performance Metals)
    type: datasheet
    url: https://www.upmet.com/sites/default/files/products/datasheet/347-datasheet.pdf
    year: 2026
  - title: Alloy 347 Stainless Steel Data Sheet, Combined Metals Company (rev 2024-01-16)
    type: datasheet
    url: https://www.combmet.com/wp-content/uploads/2024/01/Alloy-347-Stainless-Steel-Data-Sheet-2024-01-16.pdf
    year: 2024
  - title: Stainless Steel S34700 Sheet, Aalco datasheet
    type: datasheet
    url: https://www.aalco.co.uk/datasheets/Stainless-Steel-S34700-Sheet_270.ashx
  - title: 347 Stainless Technical Datasheet, Smiths Metal Centres (2023)
    type: datasheet
    url: https://www.smithmetal.com/pdf/stainless/347-stainless.pdf
    year: 2023
  - title: Bulletin 147 Type 347/347H stainless steel data sheet, Rolled Alloys (rev 03/21)
    type: datasheet
    url: https://www.rolledalloys.ca/wp-content/uploads/347_stainless-steel-data-sheet-rolled-alloys.pdf
    year: 2021
  - title: Alloy 347 UNS S34700 WNR 1.4550, Fine Tubes product page
    type: report
    url: https://www.finetubes.co.uk/products/materials/stainless-steel-tubes/alloy-347-uns-s34700-wnr-1-4550
  - title: X6CrNiNb18 10 austenitic stainless steel, Tachart material page
    type: report
    url: https://www.tachart.com/material/x6crninb18-10/
  - title: Stal nierdzewna 0H18N12Nb, 1.4550, X6CrNiNb18-10, AISI 347, AMS 5646 (Alfa-Tech datasheet)
    type: datasheet
    url: https://www.alfa-tech.com.pl/stal-nierdzewna-1-4550-1-4546-x6crninb1810-aisi-34-ams-5646-0h18n12nb/?pdf=6903
  - title: Alloys delivered from Uddeholms AB, material safety information sheet (release 2010-01-04, review 2018-09-10)
    type: sds
    url: https://www.uddeholm.com/app/uploads/sites/235/2024/05/Alloys-delivered-from-Uddeholms-AB.pdf
  - 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
  - title: 'USGS Mineral Commodity Summaries 2026: Niobium (Columbium)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
gaps:
  - No Outokumpu, ATI or Sandvik datasheet for 347 could be opened; the Outokumpu search returned no 347 page, and the ATI page was not reached. The annealed typical values come from the Combmet sheet, which cites ATI.
  - Hardness is not a canonical property name in spores/property-canon.yaml, so the benchmark is written as hardness; the three hardness rows use HB, HRB and HRBW as printed.
  - The PubChem record for nickel was blocked by a reCAPTCHA check, so the nickel GHS classes come from the Uddeholm safety information sheet for steel articles, not from PubChem or a 347 sheet. No safety data sheet for the 347 base alloy was opened.
  - The Uddeholm sheet is for Uddeholm alloys (release 2010, review 2018) and states the CLP steel rule in general terms; it is cited for the rule, not as a 347 classification.
  - 'Composition conflicts between sources: nickel is 9 to 13 % in the ASTM A240 limits (Aalco, Rolled Alloys, Alfa-Tech) but 9 to 12 % in UPMET and Combmet; silicon is 0.75 % maximum (Aalco, UPMET) but 1.00 % nominal in Combmet; phosphorus is 0.04 % (Aalco) or 0.045 % (UPMET, Rolled Alloys). The recipe uses the Aalco ASTM A240 limits and states the conflicts.'
  - The Smith datasheet prints the density as 7.93 kg/m3 and the composition row for Nb plus Ta is garbled; neither is used.
  - The UPMET table of thermal conductivity, specific heat, electrical resistivity and CTE carries no grade label, only the datasheet title; those rows are marked in their notes.
  - No cryogenic, radiation, outgassing, cold-welding or atomic-oxygen data were found for 347 in this run.
  - No critical-mineral list status for nickel, chromium or niobium was read from the official list; the USGS summaries name nickel in an executive-order context only, so critical_lists is left empty.
  - The 800 °F typical tensile value is printed in ksi and converted on import; the printed 800 °F corresponds to about 427 °C.
  - No process route (smelting, melting, refining) for 347 was read from a primary source, so the recipe has no process description.
  - Elongation and hardness values were read from different product forms (sheet, plate, strip, annealed bar); each row states its form.
  - Atomic weights were not read from a fetched page and are left out of the recipe parts.
  - Trade names beyond the generic mill names Alloy 347 and Type 347 were not found in a fetched page; the GOST and Ukrainian 08Kh18N12B code printed on a distributor page was left out because the page's composition was unreliable.
sources:
  upmet347:
    title: Datasheet for 347 Stainless Steel Sheet, Coil and Bar, AMS 5512, 5646 (United Performance Metals)
    id: AMS 5512, AMS 5646, UNS S34700
    url: https://www.upmet.com/sites/default/files/products/datasheet/347-datasheet.pdf
    year: 2026
    kind: datasheet
    license: Manufacturer datasheet, for information only (cited, not reproduced)
  combmet347:
    title: Alloy 347 Stainless Steel Data Sheet, Combined Metals Company (REV 2024 01 16)
    id: UNS S34700, EN-DIN 1.4550; typical values based on ATI source, ASTM A240
    url: https://www.combmet.com/wp-content/uploads/2024/01/Alloy-347-Stainless-Steel-Data-Sheet-2024-01-16.pdf
    year: 2024
    kind: datasheet
    license: Distributor datasheet, reference only (cited, not reproduced)
  aalco347:
    title: Stainless Steel S34700 Sheet, Aalco datasheet (ASTM A240 limits)
    id: 'Spec: ASTM A240'
    url: https://www.aalco.co.uk/datasheets/Stainless-Steel-S34700-Sheet_270.ashx
    kind: datasheet
    license: Distributor datasheet (cited, not reproduced)
  smith347:
    title: 347 Stainless Technical Datasheet, Smiths Metal Centres (2023)
    url: https://www.smithmetal.com/pdf/stainless/347-stainless.pdf
    year: 2023
    kind: datasheet
    license: Distributor datasheet, approximate testing (cited, not reproduced)
  rolled347:
    title: Bulletin No. 147, 347/347H Data Sheet, Rolled Alloys (USe 03/21)
    id: UNS S34700, S34709; AMS 5512; ASTM A240, A262; ASME SA-240
    url: https://www.rolledalloys.ca/wp-content/uploads/347_stainless-steel-data-sheet-rolled-alloys.pdf
    year: 2021
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  finetubes347:
    title: Alloy 347 UNS S34700 WNR 1.4550, Fine Tubes product page
    id: WNR 1.4550; ASTM A269, A213, A312; BS 2T66, 2T68, T72; SAE AMS 5571
    url: https://www.finetubes.co.uk/products/materials/stainless-steel-tubes/alloy-347-uns-s34700-wnr-1-4550
    kind: web
    license: Supplier web page (cited, not reproduced)
  tachart347:
    title: X6CrNiNb18 10 austenitic stainless steel, Tachart material page
    id: JIS SUS347; EN 1.4550; UNS S34700; alias Alloy 347
    url: https://www.tachart.com/material/x6crninb18-10/
    kind: web
    license: Supplier web page (cited, not reproduced)
  alfa347:
    title: Stal nierdzewna 0H18N12Nb, 1.4550, 1.4546, X6CrNiNb18-10, AISI 347, AMS 5646 (Alfa-Tech)
    id: X6CrNiNb18-10, 1.4550 EN 10088-2:2014, AISI 347, AMS 5646, TP347, S34700
    url: https://www.alfa-tech.com.pl/stal-nierdzewna-1-4550-1-4546-x6crninb1810-aisi-34-ams-5646-0h18n12nb/?pdf=6903
    kind: datasheet
    license: Supplier datasheet (cited, not reproduced)
  uddeholm-sis:
    title: Alloys delivered from Uddeholms AB, material safety information sheet (release 2010-01-04, review 2018-09-10)
    url: https://www.uddeholm.com/app/uploads/sites/235/2024/05/Alloys-delivered-from-Uddeholms-AB.pdf
    kind: datasheet
    license: Manufacturer safety information sheet (cited, not reproduced)
  usgs-nickel-2026:
    title: Mineral Commodity Summaries 2026, Nickel
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-chromium-2026:
    title: Mineral Commodity Summaries 2026, Chromium
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-niobium-2026:
    title: Mineral Commodity Summaries 2026, Niobium (Columbium)
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
license: CC-BY-4.0
updated: '2026-10-25'
review:
  status: draft
  method: assistant
  checked_values: 21
  unreachable: 2
  caveats: 6
  note: 'Values were read by an AI assistant on 2026-10-25 from the pages and PDFs named in each entry. Unreachable: PubChem (reCAPTCHA) and the Ulbrich 347 page (HTTP 403). Caveats: the datasheet values are nominal or typical values of several producers; the UPMET thermal, specific heat and resistivity tables carry no grade label; the hazard classes come from a general steel-article sheet for Uddeholm alloys; the nickel composition ranges differ between sources; the 800 °F tensile value is converted on import from ksi.'
story:
  risk_groups:
    - title: For people
      lead: Dust and fumes from working the steel carry the hazards, because the sources classify nickel, not the massive metal.
      level: 1
      verdict: Nickel classes apply to dust and fumes
      points:
        - label: Nickel in the alloy
          line: Uddeholm's safety information sheet for steel articles classes nickel with H317, H351 and H372 (DANGER). It says massive steel needs no label, but dust and fumes from grinding, polishing, welding or cutting carry the risk.
        - label: Nickel limit rule
          line: The same sheet puts steels above 10 % nickel in STOT RE1 and steels above 1 % nickel in Carcinogen Category 2. The 347 range of 9 to 13 % nickel straddles the 10 % line, so the class depends on the actual heat.
    - title: If it fails
      lead: These are failure routes printed in the sources. None is a measured space result.
      points:
        - label: Intergranular attack
          line: Combmet says the niobium addition resists intergranular corrosion after exposure at 427 to 816 °C, the range where chromium carbide forms in unstabilised grades.
        - label: Polythionic acid
          line: Rolled Alloys and Smith say 347 has good resistance to polythionic acid stress corrosion cracking, which arises in oil-refinery equipment.
        - label: Hot strength
          line: Rolled Alloys gives a typical tensile strength of 93.3 ksi at 68 °F and 69.5 ksi at 800 °F.
    - title: Handling and storage
      points:
        - label: Welds that cannot be annealed
          line: Rolled Alloys says the grade keeps good resistance to intergranular corrosion in the as-welded condition, which is why it is chosen for welded parts.
        - label: Temper
          line: Smith says the alloy is essentially non-magnetic when annealed and can only be hardened by cold working.
  why: AISI 347 is a stainless steel that keeps its corrosion resistance after welding and heating. It has 17 to 19 % chromium and 9 to 13 % nickel, and niobium (columbium) ties up the carbon so chromium carbide does not form at the grain boundaries. The UPMET datasheet prints a density of 7.96 g/cm3 for grade 347 and a melting range of 1398 to 1446 °C. Smith prints a maximum use temperature in air of 800 °C.
  uses:
    - where: Furnace and exhaust hardware
      line: UPMET lists aircraft exhaust stacks, cabin heaters, furnace heating elements and boiler casings among its industry applications for 347 sheet, coil and bar.
    - where: Refinery and reactor parts
      line: Smith lists fired heater tubes, thermowells, hanger rods and reactor components. Rolled Alloys lists recuperator tube sheets, distributor trays and equipment around reactors.
  can_do:
    - label: Carry heat in air
      value: 800 °C
      benchmark: max_service_temp
      line: Smith prints a maximum use temperature in air of 800 °C. Rolled Alloys says the grade is useful to 1500 °F for oxidation.
    - label: Resist welding damage
      value: 427 to 816 °C
      line: Combmet says the niobium stabilisation resists intergranular corrosion after exposure in the chromium-carbide range from 800 to 1500 °F.
    - label: Stiffness
      value: 193 GPa
      benchmark: elastic_modulus
      line: The modulus of elasticity at 20 °C is 193 GPa, from the Combmet datasheet.
    - label: Strength when annealed
      value: 640 MPa
      benchmark: ultimate_tensile_strength
      line: Typical annealed tensile strength is 640 MPa and typical 0.2 % yield is 250 MPa (Combmet, based on ATI data). ASTM A240 minimums are 515 MPa and 205 MPa.
  compare: Type 347 is the niobium-stabilised sibling of Type 321, which is stabilised with titanium. Rolled Alloys says 347 has slightly improved corrosion resistance over 321 in strongly oxidising environments, and that both offer good resistance to polythionic acid stress corrosion cracking. The sibling 321 profile is in this site as stainless-321.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting range
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Specify the temper and product form, because the minimums of ASTM A240 apply to sheet and the typical annealed values are for annealed material.
    - Weld in the as-welded condition where needed; the grade resists intergranular attack without re-annealing (Rolled Alloys).
    - Control dust and fumes when grinding, polishing, welding or cutting, since the Uddeholm sheet names inhalation of nickel and chromium dust and fumes as the hazard.
  good_for:
    - Welded hot-service parts that cannot be annealed afterwards, rated to 800 °C in air (Smith).
    - Refinery service where polythionic acid cracking is a concern (Rolled Alloys).
    - Heating elements, exhaust stacks and furnace parts (UPMET application list).
  watch_out:
    - 'Strength falls when hot: 93.3 ksi at 68 °F against 69.5 ksi at 800 °F (Rolled Alloys).'
    - Nickel content of 9 to 13 % puts the hazard class on the 10 % CLP line, so check the heat certificate (Uddeholm sheet).
    - Cold work is the only way to harden it, so the temper sets the strength (Smith).
    - No vacuum, radiation or atomic-oxygen data were found for this profile.
  verdict: AISI 347 is a welded, niobium-stabilised austenitic stainless steel with a printed maximum use temperature of 800 °C in air, 193 GPa modulus and typical annealed strength of 640 MPa. Its hot strength drops steeply above room temperature, its nickel content sets the hazard class of its dust and fumes, and this profile lacks space-environment numbers.
  recipe:
    line: AISI 347 is an iron-based austenitic alloy. Composition in weight percent is the ASTM A240 limits printed in the Aalco datasheet, with the niobium row from UPMET; Combmet's nominal table prints silicon 1.00 % maximum and nickel 9 to 12 %, which differ. The process route (melting and casting) was not read from a primary source.
    parts:
      - name: Iron
        symbol: Fe
        share: balance, printed as Balance in the Aalco composition table
        role: The matrix of the alloy; the other elements are dissolved in it.
      - name: Chromium
        symbol: Cr
        share: 17.00 to 19.00 wt %
        role: Gives the stainless steel its corrosion and oxidation resistance (Aalco, UPMET, Combmet).
      - name: Nickel
        symbol: Ni
        share: 9.00 to 13.00 wt % (Aalco, ASTM A240 limits); 9.00 to 12.00 wt % in UPMET and Combmet
        role: Keeps the structure austenitic and non-magnetic when annealed (Smith).
      - name: Niobium (columbium), with tantalum
        symbol: Nb
        share: 10 x C minimum to 1.00 wt % maximum (UPMET)
        role: The stabiliser that ties up carbon so that chromium carbide does not form at grain boundaries (Combmet, Rolled Alloys).
      - name: Carbon
        symbol: C
        share: 0.08 wt % maximum
        role: Kept low; niobium binds the carbon that remains.
      - name: Manganese
        symbol: Mn
        share: 2.00 wt % maximum
        role: Printed in the ASTM A240 limits; the sources read give no function for it.
      - name: Silicon
        symbol: Si
        share: 0.75 wt % maximum (Aalco, UPMET); 1.00 wt % maximum (Combmet nominal)
        role: Printed in the composition tables; the datasheets give no function.
      - name: Phosphorus
        symbol: P
        share: 0.04 wt % maximum (Aalco)
        role: An impurity limit in the ASTM A240 composition.
      - name: Sulphur
        symbol: S
        share: 0.03 wt % maximum (Aalco)
        role: An impurity limit in the ASTM A240 composition.