AISI 347H stainless steel 347H

spore: profile
id: stainless-347h
spore_version: 0.2
family: stainless-austenitic
name: AISI 347H stainless steel
abbreviation: 347H
role: High-carbon niobium-stabilised austenitic stainless steel for hot service
category: metals
type: steels-and-stainless
summary: |
  AISI 347H (UNS S34709) is the high-carbon version of AISI 347, an austenitic stainless steel stabilised with niobium (columbium) and specified with a carbon range of 0.04 to 0.10 %. A tubing supplier table for ASTM A213 347H prints a density of 7.98 kg/dm3 and a modulus of 29.0 x 10^6 psi. Goodfellow prints a modulus of 200 GPa at 20 degC, 172 GPa at 400 degC and 155 GPa at 600 degC, and a maximum use temperature in air of 850 degC. The Rolled Alloys combined 347/347H bulletin prints a 100,000-hour rupture strength of 3.55 ksi at 1400 degF and 1.95 ksi at 1500 degF. No space-environment data were found for this grade.
best_for: Welded parts for hot service in air and steam, where creep strength to 1500 degF is needed and niobium stabilisation resists intergranular attack in the as-welded condition
weakest_at: 'Strength when hot: typical tensile strength falls from 93.3 ksi at 68 degF to 69.5 ksi at 800 degF (Rolled Alloys), and no vacuum, radiation or atomic-oxygen data were found'
identity:
  formula: 'Fe-based austenitic alloy: Fe balance, Cr 17.0 to 19.0 %, Ni 9.0 to 13.0 %, C 0.04 to 0.10 %, Nb plus Ta at 8 x C minimum and 1.0 % maximum, Mn 2.0 % maximum, Si 0.75 % maximum, P 0.045 % maximum, S 0.03 % maximum'
  source: tubingchina347h
  where: C and Nb plus Ta from the ASTM A213 347/347H composition table (tubing supplier page); Cr, Ni, Mn, Si, P and S from the Rolled Alloys 347/347H composition table, which prints P 0.045 % where the tubing table prints 0.04 %
  designations:
    - system: UNS
      code: S34709
      source: tubingchina347h
      where: ASTM A213 347/347H table, UNS Designation row
    - system: AISI
      code: 347H
      source: goodfellow347h
      where: Page title, AISI 347H Stainless Steel
    - system: ASTM
      code: A213
      note: tube
      source: tubingchina347h
      where: Table heading, ASTM A213 347/347H tube composition
    - system: ASME
      code: SA-240
      note: plate, sheet and strip, combined 347/347H
      source: rolled347h
      where: 'Specifications block, ASME: SA-240'
tags:
  environments: []
  stresses: []
  applications:
    - thermal-control
    - structures
properties:
  - benchmark: density
    label: Density, grade 347H
    value: 7.98
    unit: kg/dm3
    scope: material
    conditions:
      grade: 347H (ASTM A213 tube table)
      temperature: not stated in the table
    method: Value printed in a supplier comparison table
    status: ground
    source: tubingchina347h
    where: Table 347 347H 347HFG Stainless Steel Physical Properties, row Density
  - benchmark: density
    label: Density, grade 347H (rounded)
    value: 7.9
    unit: g/cm3
    scope: material
    conditions:
      grade: 347H
      temperature: not stated
      printed_with_imperial: 0.29 lb/in3
    method: Value printed in a supplier table, rounded to one decimal by the supplier
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Density
  - benchmark: elastic_modulus
    label: Young's modulus, 20 degC
    value: 200
    unit: GPa
    scope: material
    conditions:
      grade: 347H
      temperature: 20 degC
      unit_in_source: 200 GPa / 29 x 10^6 psi
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Young's Modulus (20 degC)
  - benchmark: elastic_modulus
    label: Young's modulus, 400 degC
    value: 172
    unit: GPa
    scope: material
    conditions:
      grade: 347H
      temperature: 400 degC
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Young's Modulus (400 degC)
  - benchmark: elastic_modulus
    label: Young's modulus, 600 degC
    value: 155
    unit: GPa
    scope: material
    conditions:
      grade: 347H
      temperature: 600 degC
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Young's Modulus (600 degC)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 23 degC
    value: 14
    unit: W/m.degC
    scope: material
    conditions:
      grade: 347H
      temperature: 23 degC
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Thermal Conductivity (23 degC)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 400 degC
    value: 20
    unit: W/m.degC
    scope: material
    conditions:
      grade: 347H
      temperature: 400 degC
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Thermal Conductivity (400 degC)
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 212 degF
    value: 112.5
    unit: Btu.ft/(ft2.hr.degF)
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 212 degF
    method: Value printed in a manufacturer datasheet
    status: ground
    note: The Rolled Alloys bulletin covers 347 and 347H in one table; the values are not split by grade.
    source: rolled347h
    where: Physical Properties table, row Thermal Conductivity, column 212
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 932 degF
    value: 147.7
    unit: Btu.ft/(ft2.hr.degF)
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 932 degF
    method: Value printed in a manufacturer datasheet
    status: ground
    note: The Rolled Alloys bulletin covers 347 and 347H in one table; the values are not split by grade.
    source: rolled347h
    where: Physical Properties table, row Thermal Conductivity, column 932
  - benchmark: specific_heat
    label: Specific heat capacity, 23 degC
    value: 485
    unit: J/(kg.degC)
    scope: material
    conditions:
      grade: 347H
      temperature: 23 degC
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Specific Heat (23 degC)
  - benchmark: specific_heat
    label: Specific heat capacity, 400 degC
    value: 540
    unit: J/(kg.degC)
    scope: material
    conditions:
      grade: 347H
      temperature: 400 degC
    method: Value printed in a supplier table
    status: ground
    source: goodfellow347h
    where: Physical Properties of 347H table, row Specific Heat (400 degC)
  - benchmark: cte
    label: Coefficient of thermal expansion, 70 to 212 degF
    value: 9.2
    unit: in/in.degF x 10^-6
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature_range: 70 to 212 degF
    method: Value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Physical Properties table, row Coefficient of Thermal Expansion, column 212
  - benchmark: electrical_conductivity
    label: Electrical conductivity at 68 degF
    value: 28
    unit: '%IACS'
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 68 degF (20 degC)
    method: Value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Physical Properties table, row Electrical Conductivity
  - benchmark: melting_point
    label: Melting range, 347/347H
    value: 2550
    value_high: 2635
    bound: range
    unit: degF
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      unit_in_source: 2550 to 2635 degF
    method: Melting range printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Physical Properties header, Melting Range
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, minimum, ASTM A240
    value: 75
    bound: lower
    unit: ksi
    scope: material
    conditions:
      spec: ASTM A240
      form: sheet, plate and strip
      basis: minimum specified properties
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Mechanical Properties, Minimum Specified Properties, ASTM A 240, row Ultimate Tensile Strength
  - benchmark: yield_strength
    label: Yield strength 0.2 % offset, minimum, ASTM A240
    value: 30
    bound: lower
    unit: ksi
    scope: material
    conditions:
      spec: ASTM A240
      form: sheet, plate and strip
      measure: 0.2 % offset
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Mechanical Properties, Minimum Specified Properties, row 0.2% Yield Strength
  - benchmark: elongation
    label: Elongation, minimum, ASTM A240
    value: 40
    bound: lower
    unit: '%'
    scope: material
    conditions:
      spec: ASTM A240
      form: sheet, plate and strip
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Mechanical Properties, Minimum Specified Properties, row Elongation
  - benchmark: hardness
    label: Hardness, maximum, Brinell
    value: 201
    bound: upper
    unit: HB
    scope: material
    conditions:
      spec: ASTM A240
      scale: Brinell
    method: Maximum value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Mechanical Properties, Minimum Specified Properties, row Hardness Max, Brinell
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, ASTM A213 tube table
    value: 515
    unit: MPa
    scope: material
    conditions:
      spec: ASTM A213 tube
      grade: 347H
      note_on_page: the table does not label this value as minimum or typical
    method: Value printed in a supplier table
    status: ground
    note: The table prints 75 ksi beside 515 MPa and does not say whether it is a minimum or a typical value.
    source: tubingchina347h
    where: Mechanical Properties table, row Tensile Strength
  - benchmark: yield_strength
    label: Yield strength, ASTM A213 tube table
    value: 205
    unit: MPa
    scope: material
    conditions:
      spec: ASTM A213 tube
      grade: 347H
      note_on_page: the table does not label this value as minimum or typical
    method: Value printed in a supplier table
    status: ground
    note: The table prints 30 ksi beside 205 MPa and does not say whether it is a minimum or a typical value.
    source: tubingchina347h
    where: Mechanical Properties table, row Yield Strength
  - benchmark: elongation
    label: Elongation in 2 in, minimum, ASTM A213 tube table
    value: 35
    bound: lower
    unit: '%'
    scope: material
    conditions:
      spec: ASTM A213 tube
      gauge_length: 2 in (50.8 mm)
    method: Minimum value printed in a supplier table
    status: ground
    source: tubingchina347h
    where: Mechanical Properties table, row Elongation in 2 inches (min.)
  - benchmark: hardness
    label: Hardness, ASTM A213 tube table
    value: 192
    unit: HBW
    scope: material
    conditions:
      spec: ASTM A213 tube
      grade: 347H
    method: Value printed in a supplier table; its column header is printed as Harndess HBW
    status: ground
    source: tubingchina347h
    where: Mechanical Properties table, column Hardness HBW
  - benchmark: ultimate_tensile_strength
    label: Typical tensile strength at 68 degF
    value: 93.3
    unit: ksi
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 68 degF
      basis: typical tensile and impact properties
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Typical Tensile and Impact Properties table, column 68, row Ultimate Tensile Strength
  - benchmark: ultimate_tensile_strength
    label: Typical tensile strength at 800 degF
    value: 69.5
    unit: ksi
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 800 degF (about 427 degC)
      basis: typical tensile and impact properties
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Typical Tensile and Impact Properties table, column 800, row Ultimate Tensile Strength
  - benchmark: yield_strength
    label: Typical 0.2 % yield strength at 68 degF
    value: 36.5
    unit: ksi
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 68 degF
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Typical Tensile and Impact Properties table, column 68, row 0.2% Yield Strength
  - benchmark: yield_strength
    label: Typical 0.2 % yield strength at 800 degF
    value: 29.7
    unit: ksi
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      temperature: 800 degF (about 427 degC)
    method: Typical value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Typical Tensile and Impact Properties table, column 800, row 0.2% Yield Strength
  - benchmark: max_service_temp
    label: Maximum use temperature in air
    value: 850
    unit: degC
    scope: material
    conditions:
      environment: air
      basis: stated as the upper service limit, no duration given
    method: Value printed on a supplier page for 347H
    status: ground
    source: goodfellow347h
    where: 'Section 4.3, bullet Air: up to 850 degC (1,560 degF)'
  - benchmark: max_service_temp
    label: Maximum use temperature in steam
    value: 750
    unit: degC
    scope: material
    conditions:
      environment: steam
      basis: stated as the upper service limit, no duration given
    method: Value printed on a supplier page for 347H
    status: ground
    source: goodfellow347h
    where: 'Section 4.3, bullet Steam: up to 750 degC (1,380 degF)'
  - benchmark: max_service_temp
    label: Useful temperature for oxidation resistance
    value: 1500
    unit: degF
    scope: material
    conditions:
      grade: 347/347H combined bulletin
      environment: air, oxidation
    method: Value printed in a manufacturer datasheet
    status: ground
    source: rolled347h
    where: Opening paragraph, sentence Useful to 1500 degF
  - benchmark: creep_rupture_strength_100000h
    label: Average extrapolated 100,000-hour rupture strength at 1400 degF
    value: 3.55
    unit: ksi
    scope: material
    conditions:
      grade: 347 and 347H (combined row)
      temperature: 1400 degF
      basis: average extrapolated 100,000-hour rupture strength
    method: Value printed in a manufacturer table; the table notes that extrapolation to 100,000 hours is not good practice above 1800 degF
    status: ground
    source: rolledrupture
    where: Table Rupture Strength, row 347, 347H, column 1400
  - benchmark: creep_rupture_strength_100000h
    label: Average extrapolated 100,000-hour rupture strength at 1500 degF
    value: 1.95
    unit: ksi
    scope: material
    conditions:
      grade: 347 and 347H (combined row)
      temperature: 1500 degF
      basis: average extrapolated 100,000-hour rupture strength
    method: Value printed in a manufacturer table
    status: ground
    source: rolledrupture
    where: Table Rupture Strength, row 347, 347H, column 1500
corrosion:
  - environment: Chromium-carbide sensitisation range, about 427 to 850 degC (welding and stress relief)
    headline: Niobium stabilisation keeps the grade resistant to intergranular attack after exposure in the sensitisation range, so welded parts usually need no re-annealing.
    effect: Goodfellow says the niobium addition resists intergranular attack in the sensitisation range of about 427 to 850 degC and that stabilisation removes the need for post-weld annealing in most service conditions. 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
    source: goodfellow347h
    where: Section 1 (sensitisation range) and Section 6 (welding)
  - environment: Polythionic acid in oil refineries
    headline: The 347 and 347H grades resist 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. The bulletin prints no test duration, concentration or crack data.
    rating: low
    conditions:
      basis: datasheet statement for the combined 347/347H bulletin
    source: rolled347h
    where: Opening paragraph and Applications list
  - environment: Strongly oxidising service in air up to 1500 degF
    headline: The grade has slightly better corrosion resistance than type 321 in strongly oxidising environments.
    effect: Rolled Alloys says type 347 has slightly improved corrosion resistance over type 321 in strongly oxidising environments, and that its high-temperature oxidation resistance is similar to that of 304 stainless steel. No oxidation rate is printed.
    rating: low
    conditions:
      basis: datasheet statements for the combined 347/347H bulletin
    source: rolled347h
    where: Opening paragraph
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 sheet is for Uddeholm alloys, not a 347H sheet.'
      ghs:
        - H317
        - H351
        - H372
      source: uddeholm-sis
      where: Section 2.3, nickel entry
    - text: 'The same sheet quotes the CLP rule for steels: more than 10 % nickel is STOT RE1, 1 to 10 % nickel is STOT RE2, and more than 1 % nickel is Carcinogen Category 2. Grade 347H has 9 to 13 % nickel, which straddles the 10 % line, so the class depends on the actual heat.'
      ghs: []
      source: uddeholm-sis
      where: Section 2.3, note under the nickel entry
    - text: 'Chromium entry of the same sheet: H317 May cause an allergic skin reaction. H350i May cause cancer by inhalation. H410 Very toxic to aquatic life with long lasting effects.'
      ghs:
        - H317
        - H350i
        - H410
      source: uddeholm-sis
      where: Section 2.3, chromium entry
    - text: The sheet says alloys containing nickel or chromium may cause health hazards by inhalation of dusts and fumes produced by grinding, polishing, welding or cutting, and that prolonged or repeated skin contact may cause dermatitis in nickel-sensitised persons. Massive steel products do not need a label.
      ghs: []
      source: uddeholm-sis
      where: Section 2.3 and Section 3.1, Description of Hazards
  failure_risks:
    - mode: Intergranular attack from chromium carbide
      trigger: Exposure in the sensitisation range of about 427 to 850 degC, for example after welding, when the carbon is not tied up by niobium
      consequence: Chromium carbide forms at grain boundaries and the metal loses intergranular corrosion resistance. Goodfellow says the niobium addition prevents this.
      severity: moderate
      source: goodfellow347h
      where: Section 1
    - mode: Polythionic acid stress corrosion cracking
      trigger: Polythionic acid formed in oil-refinery equipment
      consequence: Rolled Alloys says the grade has good resistance to this cracking. The bulletin prints no crack or failure data.
      severity: moderate
      source: rolled347h
      where: Opening paragraph and Applications list
    - mode: Loss of strength when hot
      trigger: Service at 800 degF and above
      consequence: Typical tensile strength falls from 93.3 ksi at 68 degF to 69.5 ksi at 800 degF, and typical 0.2 % yield falls from 36.5 ksi to 29.7 ksi over the same range. The 100,000-hour rupture strength is 1.95 ksi at 1500 degF.
      severity: low
      source: rolled347h
      where: Typical Tensile and Impact Properties table, columns 68 and 800
  side_effects: []
  handling:
    - text: Weld in the as-welded condition where possible. Rolled Alloys says the grade keeps good resistance to intergranular corrosion without re-annealing.
      source: rolled347h
      where: Features list
    - text: Goodfellow prefers gas tungsten arc welding (TIG) for this grade and says niobium stabilisation removes the need for post-weld annealing in most service conditions.
      source: goodfellow347h
      where: Section 6, Welding
    - text: The Uddeholm sheet says dust and fume exposure from grinding, polishing, welding or cutting should be controlled, and that personal protective equipment must be used.
      source: uddeholm-sis
      where: Section 3.1, Specific process and exposure controls, and Handling and Storage
    - text: Specify the carbon range and product form. The ASTM A213 values are for tube, and the ASTM A240 minimums are for sheet, plate and strip.
      source: tubingchina347h
      where: Table headings
  mitigations: []
uses:
  - application: thermal-control
    device: Fired heater tubes and recuperator tube sheets in refineries
    example: Rolled Alloys lists fired heater tubes, recuperator tube sheets, shells and supports for the 347/347H grade, and says 347 is especially suited where temperatures exceed 550 degF and sulfidation resistance is needed.
    source: rolled347h
    where: Applications list of the Rolled Alloys bulletin
  - application: structures
    device: Hanger rods, distributor trays and thermowells
    example: Rolled Alloys lists hanger rods, distributor trays, thermowells and equipment in and around reactors as applications for the 347/347H grade.
    source: rolled347h
    where: Applications list of the Rolled Alloys bulletin
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 approximately 60 % of apparent consumption in 2025.'
    substitutes:
      - 'USGS: low-nickel, duplex, or ultrahigh-chromium stainless steels have been substituted for austenitic grades in petrochemical industries; 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 column, world total 3,900,000; 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, chromite ore, 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, or in superalloys.'
    source: usgs-chromium-2026
    where: World Mine Production and Reserves table, 2025e column, world total 51,000; shares calculated by Space Mushroom from the country values 23,000; 9,000; 7,000; 3,000 (table units as printed). Recycling; Substitutes.
  - 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: niobium was recycled when niobium-bearing steels and superalloys were recycled; scrap recovery specifically for niobium content was negligible.'
    substitutes:
      - 'USGS: molybdenum, tantalum and titanium as alloying elements in stainless and high-strength steels, and ceramic matrix composites, molybdenum, tantalum and tungsten in high-temperature superalloys, can replace niobium with a performance loss or higher cost.'
    source: usgs-niobium-2026
    where: World Mine Production and Reserves table, 2025e column, world total 112,000; shares calculated by Space Mushroom from the country values 104,000; 6,000; 970. Recycling; Substitutes.
documents:
  - title: Rolled Alloys Bulletin No. 147, 347/347H data sheet (rev. 03/21)
    type: datasheet
    url: https://www.rolledalloys.ca/wp-content/uploads/347_stainless-steel-data-sheet-rolled-alloys.pdf
    year: 2021
  - title: Rolled Alloys rupture strength table, 100,000-hour extrapolated values
    type: datasheet
    url: https://www.rolledalloys.ca/wp-content/uploads/2022/07/Rupture_Strength_PDF.pdf
    year: 2022
  - title: Tubing supplier comparison of 347, 347H and 347HFG, ASTM A213 tables
    type: datasheet
    url: https://tubingchina.com/347-vs-347h-vs-347hfg.htm
  - title: 'Goodfellow: AISI 347H stainless steel, properties, processing and applications'
    type: report
    url: https://www.goodfellow.com/uk/resources/aisi-347h-stainless-steel-properties-processing-applications/
  - 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
    year: 2018
  - 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 manufacturer datasheet for 347H from ATI, Outokumpu, Alleima or Sandvik could be opened. The ATI 347 page covers UNS S34700 only and links to a PDF that was not reachable. Totalmateria pages show property names but their values sit behind a registration wall.
  - The Goodfellow mechanical table is attributed to a named product (Alleima 8R40) and is not labelled as 347H, so it is not used. Its physical table is labelled as 347H and is used.
  - The Rolled Alloys bulletin covers 347 and 347H in one table. Its melting range, thermal conductivity, expansion, electrical conductivity, minimum specified properties, typical hot strength and rupture values are for the combined grade, and each row says so in its conditions.
  - The tubing supplier table prints 515 MPa, 205 MPa and 192 HBW without saying whether they are minimum or typical, and its hardness column header is printed as Harndess HBW.
  - 'Composition conflicts between sources: chromium is 17.0 to 19.0 % in the Rolled Alloys table but 17.0 to 20.0 % in the tubing supplier table; nickel is 9.0 to 13.0 % in both but 11.0 % nominal in Goodfellow; phosphorus is 0.045 % in Rolled Alloys and 0.04 % in the tubing table. The recipe uses the Rolled Alloys ranges for the elements it gives and the tubing table for carbon and niobium.'
  - The EN number for 347H was not confirmed. The 1.4550 number belongs to 347, not 347H. A search returned a supplier cross-reference that gives 1.4912 for X7CrNiNb18-10, but that snippet was not confirmed on a fetched page, so no EN designation is listed.
  - 'Density differs between sources: 7.98 kg/dm3 (tubing table) and 7.9 g/cm3 (Goodfellow, rounded). Both are kept with their sources.'
  - Modulus of 29.0 x 10^6 psi from the tubing table is about 200 GPa and is not listed separately; the Goodfellow value of 200 GPa is used.
  - Electrical conductivity (28 %IACS) and creep rupture strength (100,000 hours) are not canonical property names in spores/property-canon.yaml. They are written as electrical_conductivity and creep_rupture_strength_100000h, and the Rolled Alloys rupture values are for 347 and 347H together.
  - Hardness is not a canonical property name in spores/property-canon.yaml, so the benchmark is written as hardness.
  - The Goodfellow maximum service temperature of 850 degC in air is a supplier statement for 347H. It is higher than the 800 degC printed for 347 in the stainless-347 profile, and no datasheet with a stated duration was read for 347H.
  - Creep and rupture data for 347H alone were not found on a fetched page. The Rolled Alloys figures are extrapolated averages for 347 and 347H together, and the bulletin says extrapolation to 100,000 hours is not good practice above 1800 degF.
  - No critical-mineral list status for nickel, chromium or niobium was read from the official USGS 2025 list or the EU list. critical_lists is left empty for all three.
  - PubChem records for nickel were not opened in this run. The hazard classes come from the Uddeholm safety information sheet for steel articles, which covers Uddeholm alloys and not a 347H sheet.
  - No process route (melting, casting) for 347H was read from a primary source, so the recipe has no process description.
  - Atomic weights were not read from a fetched page and are left out of the recipe parts.
  - No cryogenic, radiation, outgassing, cold-welding, vacuum or atomic-oxygen data were found for 347H.
  - The makeitfrom AISI 347H page returned HTTP 403 and was not read.
  - The tubing supplier page refuses plain curl requests (HTTP 406), so verify-values cannot read it. Its five mechanical and physical values and its UNS and A213 designations were checked by hand against the page text fetched with browser request headers.
sources:
  tubingchina347h:
    title: 347 vs 347H vs 347HFG, tubing supplier comparison with ASTM A213 347H composition, physical and mechanical tables
    id: UNS S34709; ASTM A213 347/347H
    url: https://tubingchina.com/347-vs-347h-vs-347hfg.htm
    kind: web
    license: Supplier web page (cited, not reproduced)
  goodfellow347h:
    title: 'AISI 347H Stainless Steel: properties, processing and applications (Goodfellow)'
    id: AISI 347H
    url: https://www.goodfellow.com/uk/resources/aisi-347h-stainless-steel-properties-processing-applications/
    kind: web
    license: Supplier web page (cited, not reproduced)
  rolled347h:
    title: Bulletin No. 147, 347/347H Data Sheet (Rolled Alloys, rev. 03/21)
    id: UNS S34700, S34709; ASME SA-240; ASTM A240, A262
    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)
  rolledrupture:
    title: Rupture Strength, average extrapolated 100,000-hour rupture strength table (Rolled Alloys)
    id: Rolled Alloys rupture table, rows 347, 347H
    url: https://www.rolledalloys.ca/wp-content/uploads/2022/07/Rupture_Strength_PDF.pdf
    year: 2022
    kind: datasheet
    license: Manufacturer table (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
    year: 2018
    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: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 31
  unreachable: 1
  caveats: 6
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: makeitfrom AISI 347H page (HTTP 403). Caveats: the Rolled Alloys values cover 347 and 347H together; the tubing table does not label tensile, yield or hardness values as minimum or typical; the hazard classes come from a general steel-article sheet for Uddeholm alloys; the chromium and nickel ranges differ between sources; the 850 degC air limit is a supplier statement.'
story:
  recipe:
    line: 'AISI 347H is an iron-based austenitic alloy. It is the high-carbon form of AISI 347: carbon is specified at 0.04 to 0.10 %, and niobium at a minimum of 8 times the carbon content (to 1.0 % maximum with tantalum) ties the carbon up. The process route (melting and casting) was not read from a primary source.'
    parts:
      - name: Iron
        symbol: Fe
        share: balance
        role: The matrix of the alloy; the other elements are dissolved in it.
      - name: Chromium
        symbol: Cr
        share: 17.0 to 19.0 wt % (Rolled Alloys)
        role: Gives the stainless steel its corrosion and oxidation resistance.
      - name: Nickel
        symbol: Ni
        share: 9.0 to 13.0 wt %
        role: Part of the austenitic structure. The sources read name no separate function for it.
      - name: Carbon
        symbol: C
        share: 0.04 to 0.10 wt % (tubing table, ASTM A213 347H)
        role: Higher carbon than 347. Niobium ties up the carbon so that chromium carbide does not form at grain boundaries (Goodfellow).
      - name: Niobium (columbium), with tantalum
        symbol: Nb
        share: 8 x C minimum to 1.0 wt % maximum
        role: The stabiliser. It keeps chromium carbide from forming at grain boundaries in the sensitisation range (Goodfellow).
      - name: Manganese
        symbol: Mn
        share: 2.0 wt % maximum
        role: Printed as a maximum in the composition tables; the sources read give no function for it.
      - name: Silicon
        symbol: Si
        share: 0.75 wt % maximum
        role: Printed as a maximum in the composition tables; the sources read give no function for it.
      - name: Phosphorus
        symbol: P
        share: 0.045 wt % maximum (Rolled Alloys)
        role: Impurity limit in the composition tables.
      - name: Sulphur
        symbol: S
        share: 0.03 wt % maximum
        role: Impurity limit in the composition tables.
  risk_groups:
    - title: For people
      lead: Dust and fumes from working the steel carry the hazards, because the sources classify nickel and chromium, not the massive metal.
      level: 1
      verdict: Nickel and chromium 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 347H 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: Goodfellow says the niobium addition resists intergranular corrosion after exposure at about 427 to 850 degC, the range where chromium carbide forms in unstabilised grades.
        - label: Polythionic acid
          line: Rolled Alloys says the grade 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 degF and 69.5 ksi at 800 degF, and a 100,000-hour rupture strength of 1.95 ksi at 1500 degF.
    - 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, and Goodfellow says stabilisation removes the need for post-weld annealing in most service conditions.
        - label: Dust control
          line: The Uddeholm sheet says dust and fume exposure should be controlled and that personal protective equipment must be used during grinding, polishing, welding or cutting.
  why: AISI 347H is a stainless steel for hot service that keeps its corrosion resistance after welding and heating. It has 17 to 19 % chromium and 9 to 13 % nickel, with a higher carbon range (0.04 to 0.10 %) than AISI 347. Niobium ties up the carbon so that chromium carbide does not form at the grain boundaries. Goodfellow prints a maximum use temperature in air of 850 degC for 347H, and the Rolled Alloys bulletin gives creep strength up to 1500 degF.
  uses:
    - where: Refinery heaters and recuperators
      line: Rolled Alloys lists fired heater tubes and recuperator tube sheets, shells and supports among the applications of the 347/347H grade, and says 347 is especially suited where temperatures exceed 550 degF and sulfidation resistance is needed.
    - where: Hangers, trays and reactor equipment
      line: The same bulletin lists hanger rods, distributor trays, thermowells and equipment in and around reactors, where the grade's resistance to polythionic acid is relevant.
  can_do:
    - label: Carry heat in air
      value: 850 degC
      benchmark: max_service_temp
      line: Goodfellow prints a maximum use temperature in air of 850 degC for 347H, and 750 degC in steam. Rolled Alloys says the 347/347H grade is useful to 1500 degF for oxidation.
    - label: Resist welding damage
      value: Niobium stabilised
      line: Goodfellow says niobium stabilisation resists intergranular corrosion after exposure in the sensitisation range of about 427 to 850 degC, and Rolled Alloys says the grade keeps good resistance in the as-welded condition.
    - label: Stiffness
      value: 200 GPa
      benchmark: elastic_modulus
      line: The Young's modulus at 20 degC is 200 GPa, from the Goodfellow 347H table. It falls to 172 GPa at 400 degC and 155 GPa at 600 degC.
    - label: Typical tensile strength
      value: 93.3 ksi at 68 degF
      benchmark: ultimate_tensile_strength
      line: Typical tensile strength at 68 degF is 93.3 ksi for the 347/347H grade, falling to 69.5 ksi at 800 degF (Rolled Alloys). The ASTM A213 tube table prints 515 MPa.
  compare: AISI 347H is the high-carbon version of AISI 347. Its carbon range is 0.04 to 0.10 %, a higher range than 347, and it has its own UNS number, S34709. Rolled Alloys prints both grades on one bulletin, and its niobium rule for 347H is 8 times the carbon content instead of 10 times. Both grades resist polythionic acid stress corrosion cracking. The sibling 347 profile is in this site as stainless-347.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting range
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Specify the carbon range and the product form, since the ASTM A213 values are for tube and the ASTM A240 minimums are for sheet, plate and strip.
    - Weld in the as-welded condition where possible; Goodfellow prefers TIG welding for this grade.
    - 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:
    - High-temperature welded parts in air and steam, rated to 850 degC in air (Goodfellow).
    - Refinery service where polythionic acid cracking is a concern (Rolled Alloys).
    - Fired heater tubes and recuperator tube sheets (Rolled Alloys application list).
  watch_out:
    - 'Strength falls when hot: 93.3 ksi at 68 degF against 69.5 ksi at 800 degF (Rolled Alloys).'
    - Nickel content of 9 to 13 % puts the hazard class on the 10 % CLP line, so check the heat certificate (Uddeholm sheet).
    - Many values are for 347 and 347H together, so check the tube or sheet table that matches the product you buy.
    - No vacuum, radiation or atomic-oxygen data were found for this profile.
  verdict: AISI 347H is the high-carbon, niobium-stabilised version of 347, with a 200 GPa modulus at 20 degC and a supplier-stated use limit of 850 degC in air. Its hot strength falls steeply above room temperature, its nickel content sets the hazard class of its dust and fumes, and this profile lacks space-environment numbers.