spore: profile
id: super-invar-32-5
spore_version: 0.2
family: nickel-alloys
name: Super Invar 32-5
abbreviation: Super Invar
role: low-expansion structural alloy
category: metals
type: nickel-superalloys
summary: |
  Super Invar 32-5 is an iron-nickel-cobalt alloy with a nominal 32.00 % nickel and 5.50 % cobalt, balance iron, that Carpenter Technology designs to give minimum thermal expansion at room temperatures. Hi-Temp Metals prints a mean coefficient of thermal expansion of 0.63 ppm/°C from -55 to 95 °C and a density of 8150 kg/m3. The typical yield strength is 276 MPa in the annealed condition. The 1972 JPL telescope study did not use it, because its expansion properties were unstable over long periods.
best_for: Parts that must hold a length near room temperature, where Carpenter says its thermal expansion is less than that of Invar 36 over -67 to 203 °F (-55 to 95 °C)
weakest_at: Long-term expansion stability (the reason the 1972 JPL study gave for not using it), and oxidation during heat treatment above about 1000 °F (538 °C)
identity:
  formula: 'Fe-32Ni-5.5Co (Super Invar 32-5): iron balance, nickel 32.00 %, cobalt 5.50 %, manganese 0.40 %, silicon 0.25 %, carbon 0.02 % (Carpenter nominal type analysis); UNS K93500'
  source: carpenter-super-invar
  where: Type analysis table, page 1 (nominal values, weight %); UNS K93500 on the same page under Associated specifications
  designations:
    - system: UNS
      code: K93500
      source: carpenter-super-invar
      where: Page 1, Associated specifications line
    - system: ASTM
      code: F1684
      note: applicable designation for this alloy
      source: carpenter-super-invar
      where: Page 1, Applicable designation line
    - system: Trade name
      code: Super Invar 32-5
      source: carpenter-super-invar
      where: Page 1 title
tags:
  environments: []
  stresses:
    - extreme-cold
  applications:
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: density
    value: 8150
    unit: kg/m3
    scope: material
    conditions:
      form: not stated
      unit_in_source: 8150 kg/cu m
    method: Value printed in a supplier technical data table
    status: ground
    source: hightempmetals-super-invar
    where: Physical Properties table, row Density, metric line
  - benchmark: density
    value: 0.294
    unit: lb/in3
    scope: material
    conditions:
      form: not stated
      unit_in_source: 0.2940 lb/in3, English Units column
    method: Value printed in the manufacturer's physical properties table
    status: ground
    source: carpenter-super-invar
    where: Physical properties table (page 2), row DENSITY, English Units column
  - benchmark: specific_gravity
    label: Specific gravity (custom name, not in property-canon)
    value: 8.15
    unit: '-'
    scope: material
    conditions:
      printed_in: English and metric columns, both printed as 8.15
    method: Value printed in the manufacturer's physical properties table
    status: ground
    source: carpenter-super-invar
    where: Physical properties table (page 2), row SPECIFIC GRAVITY
  - benchmark: cte
    value: 0.63
    unit: ppm/°C
    scope: material
    conditions:
      temperature_range: '-55 to 95 °C'
      basis: mean coefficient of thermal expansion
      unit_in_source: 0.63 under the column heading 10(-6)/°C
    method: Value printed in a supplier technical data table
    status: ground
    source: hightempmetals-super-invar
    where: Physical Properties table, row Mean coefficient of thermal expansion, 10(-6)/°C line for -55 to 95°C
  - benchmark: poissons_ratio
    value: 0.23
    unit: '-'
    scope: material
    conditions:
      basis: printed with no unit
    method: Value printed in the manufacturer's physical properties table
    status: ground
    source: carpenter-super-invar
    where: Physical properties table (page 2), row POISSON'S RATIO, English Units column
  - benchmark: electrical_resistivity
    value: 481.3
    unit: ohm-cir-mil/ft
    scope: material
    conditions:
      temperature: 73 °F (23 °C)
    method: Value printed in the manufacturer's physical properties table
    status: ground
    source: carpenter-super-invar
    where: Physical properties table (page 2), row ELECTRICAL RESISTIVITY, 73°F (23°C) line
  - benchmark: electrical_resistivity
    value: 80
    unit: µΩ·cm
    scope: material
    conditions:
      temperature: room temperature (RT), as printed
    method: Value printed in a supplier technical data table
    status: ground
    source: hightempmetals-super-invar
    where: Physical Properties table, row Electrical resistivity (RT)
  - benchmark: martensite_start
    label: Martensite start temperature (custom name, not in property-canon)
    value: -80
    unit: °C
    scope: material
    conditions:
      printed_as: '-112 °F and -80 °C'
    method: Value printed in the manufacturer's physical properties table
    status: ground
    source: carpenter-super-invar
    where: Physical properties table (page 2), row MARTENSITE START, metric column
  - benchmark: yield_strength
    value: 276
    unit: MPa
    scope: material
    conditions:
      heat_treatment: annealed
      basis: typical mechanical properties table, 0.2% yield
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Annealed, 0.2% YIELD STRENGTH, MPa column
  - benchmark: yield_strength
    value: 276
    unit: MPa
    scope: material
    conditions:
      heat_treatment: cold worked
      basis: typical mechanical properties table, 0.2% yield
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Cold worked, 0.2% YIELD STRENGTH, MPa column
  - benchmark: ultimate_tensile_strength
    value: 483
    unit: MPa
    scope: material
    conditions:
      heat_treatment: annealed
      basis: typical mechanical properties table
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Annealed, ULTIMATE TENSILE STRENGTH, MPa column
  - benchmark: ultimate_tensile_strength
    value: 483
    unit: MPa
    scope: material
    conditions:
      heat_treatment: cold worked
      basis: typical mechanical properties table
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Cold worked, ULTIMATE TENSILE STRENGTH, MPa column
  - benchmark: elongation
    value: 40
    unit: '%'
    scope: material
    conditions:
      heat_treatment: annealed
      gauge: 2 in (50.8 mm)
      basis: typical mechanical properties table
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Annealed, ELONGATION IN 2 IN (50.8 MM) column
  - benchmark: elongation
    value: 40
    unit: '%'
    scope: material
    conditions:
      heat_treatment: cold worked
      gauge: 2 in (50.8 mm)
      basis: typical mechanical properties table
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Cold worked, ELONGATION IN 2 IN (50.8 MM) column
  - benchmark: hardness_rockwell_b
    label: Hardness, Rockwell B (custom name, not in property-canon)
    value: 75
    unit: HRB
    scope: material
    conditions:
      heat_treatment: annealed
      basis: typical mechanical properties table
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Annealed, HARDNESS HRB column
  - benchmark: hardness_rockwell_b
    label: Hardness, Rockwell B (custom name, not in property-canon)
    value: 90
    unit: HRB
    scope: material
    conditions:
      heat_treatment: cold worked
      basis: typical mechanical properties table
    method: Typical value printed in the manufacturer's mechanical properties table
    status: ground
    source: carpenter-super-invar
    where: Typical mechanical properties table (page 3), row Cold worked, HARDNESS HRB column
corrosion:
  - environment: Heat treatment at or above about 1000 °F (538 °C)
    headline: Super Invar 32-5 oxidises readily above about 1000 °F (538 °C), so heat treatment needs a protective atmosphere.
    effect: Carpenter says the alloy oxidises readily at heat-treating temperatures above about 1000 °F (538 °C) and recommends vacuum, hydrogen, dissociated ammonia or inert gases.
    rating: moderate
    conditions:
      process: heat treatment at or above about 1000 °F (538 °C)
    source: carpenter-super-invar
    where: Heat treatment section (page 3), paragraph on protective environments
  - environment: Forging furnace with a long soak
    headline: A long soak in the forging furnace can leave a checked surface.
    effect: Carpenter says long soaking may give a checked surface from oxygen and sulfur contamination, and suggests forging at 2000/2150 °F (1093/1177 °C).
    rating: moderate
    conditions:
      process: forging
    source: carpenter-super-invar
    where: Workability, Forging paragraph (page 4)
  - environment: Humid air and corrosion protection (no test of Super Invar 32-5 read)
    headline: No humidity or salt-spray test of Super Invar 32-5 was read; the datasheet names plating and zinc coating as the usual finishes.
    effect: Carpenter says the alloy can be chromium, cadmium and nickel plated or zinc coated by the usual methods used for ferrous alloys. No corrosion rate or humidity rating is printed for the bare alloy.
    rating: unknown
    conditions:
      basis: datasheet statement on finishes; no corrosion test data
    source: carpenter-super-invar
    where: Workability, Plating paragraph (page 4)
risks:
  hazards:
    - text: |
        Cobalt is the main hazard in this alloy. PubChem's aggregation of ECHA C&L notifications for cobalt gives H317 (more than 99.9 %, may cause an allergic skin reaction), H334 (more than 99.9 %, may cause allergy or asthma symptoms if inhaled), H341 (65.8 %), H350 (64.5 %) and H360F (61.6 %). These are ratios for the element, not for Super Invar 32-5 itself.
      ghs:
        - H317
        - H334
        - H341
        - H350
        - H360F
      source: pubchem-cobalt
      where: Safety and Hazards, GHS Classification (CID 104730), aggregated ECHA C&L notifications
    - text: |
        Nickel (32.00 % of the alloy) is also a sensitiser. PubChem's aggregation of ECHA C&L notifications for nickel gives H317 for 99.9 % of reports, H372 (damage to organs through prolonged or repeated exposure) for 99.7 %, and H351 (suspected of causing cancer) for 72.9 %.
      ghs:
        - H317
        - H372
        - H351
      source: pubchem-nickel
      where: Safety and Hazards, GHS Classification (CID 935), aggregated ECHA C&L notifications
  failure_risks:
    - mode: Dimensional drift after fabrication
      trigger: Machining, forming or deep drawing introduces stresses
      consequence: Carpenter says fabricating stresses promote variation in thermal expansion behaviour, so parts should be heat treated at or as close to finish size as possible.
      severity: moderate
      source: carpenter-super-invar
      where: Heat treatment section (page 3), first paragraph
    - mode: Transformation at low temperature
      trigger: Service below -67 °F (-55 °C)
      consequence: Carpenter gives austenite stability to service temperatures of at least -67 °F (-55 °C) and prints martensite start at -112 °F (-80 °C); the datasheet gives no expansion values below -67 °F (-55 °C).
      severity: moderate
      source: carpenter-super-invar
      where: Description (page 1) and Physical properties table (page 2), row MARTENSITE START
    - mode: Checked surface from furnace soaking
      trigger: Long soak in a forging furnace
      consequence: Carpenter says a long soaking time may give a checked surface from oxygen and sulfur contamination.
      severity: moderate
      source: carpenter-super-invar
      where: Workability, Forging paragraph (page 4)
    - mode: Grain boundary embrittlement after machining
      trigger: Residual sulfur left on machined parts
      consequence: Carpenter says residual sulfur can cause grain boundary embrittlement, so parts should be degreased and cleaned as soon after machining as possible.
      severity: moderate
      source: carpenter-super-invar
      where: Machinability, additional notes (page 4)
  side_effects:
    - text: Machined chips are gummy and stringy, so the alloy is somewhat difficult to machine.
      affects: Machining operations
      source: carpenter-super-invar
      where: Machinability paragraph (page 4)
  handling:
    - text: 'Heat-treat before final machining: heat to 1550 °F (843 °C) for 1 hour, water quench, stress-relieve at 600 °F (316 °C) for 1 hour, air cool, then age at 200 °F (93 °C) for 24 hours and air cool.'
      source: carpenter-super-invar
      where: Heat treatment, heat treating for lowest thermal expansion (page 3)
    - text: Above about 1000 °F (538 °C), heat-treat in a protective environment such as vacuum, hydrogen, dissociated ammonia or inert gas.
      source: carpenter-super-invar
      where: Heat treatment section (page 3)
    - text: Forge at 2000/2150 °F (1093/1177 °C), heat rapidly and avoid soaking in the forging furnace.
      source: carpenter-super-invar
      where: Workability, Forging paragraph (page 4)
    - text: Degrease and clean machined parts as soon as possible after machining to remove residual sulfur.
      source: carpenter-super-invar
      where: Machinability, additional notes (page 4)
  mitigations:
    - text: Heat-treat parts at or as close to finish size as possible, using the schedule under handling.
      source: carpenter-super-invar
      where: Heat treatment section (page 3)
uses:
  - application: optics-and-cameras
    device: Optical and laser systems
    example: Carpenter lists optical and laser systems as an application of Super Invar 32-5 on its datasheet.
    source: carpenter-super-invar
    where: Description (page 1), Applications list
  - application: electronics-and-chips
    device: Semiconductor components
    example: Carpenter lists semiconductor components among the applications of Super Invar 32-5 on its datasheet.
    source: carpenter-super-invar
    where: Description (page 1), Applications list
  - application: electronics-and-chips
    device: Wave guide tubes and other low-expansion glass or quartz assemblies
    example: Carpenter lists wave guide tubes and other systems with low expansion glass or quartz assemblies as applications.
    source: carpenter-super-invar
    where: Description (page 1), Applications list
supply:
  - subject: Nickel (32.00 % of the alloy)
    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: Canada
        share_percent: 3.6
        year: 2025
      - country: New Caledonia
        share_percent: 3.6
        year: 2025
      - country: China
        share_percent: 3.1
        year: 2025
    critical_lists:
      - list: 'USGS MCS 2026 nickel chapter: the Executive Order 14285 text names critical minerals such as nickel'
        listed: true
    recycling: 'USGS: in 2025 nickel recovered from scrap accounted for approximately 60% of apparent consumption.'
    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-nickel-2026
    where: World Mine Production and Reserves table, 2025e column (world total 3,900,000 t); shares computed by Space Mushroom from that table; Recycling and Substitutes paragraphs; critical-minerals wording in the Events section
  - subject: Cobalt (5.50 % of the alloy)
    producers:
      - country: Congo (Kinshasa)
        share_percent: 73
        year: 2025
      - country: Indonesia
        share_percent: 14
        year: 2025
    recycling: 'USGS: in 2025, cobalt content of purchased scrap represented 25% of estimated cobalt consumption.'
    substitutes:
      - 'USGS: depending on the application, substitution for cobalt could result in a loss in product performance or increased cost.'
    source: usgs-cobalt-2026
    where: Events, Trends, and Issues paragraph (shares printed as 73% and 14% of world total); Recycling line; Substitutes paragraph; World Mine Production table, 2025 column (world total 310,000 t)
  - subject: Iron (balance of the alloy)
    producers:
      - country: Australia
        share_percent: 37.7
        year: 2025
      - country: Brazil
        share_percent: 16.2
        year: 2025
      - country: India
        share_percent: 11.9
        year: 2025
      - country: China
        share_percent: 11.2
        year: 2025
    recycling: 'USGS: none for iron ore; see the separate Iron and Steel Scrap chapter.'
    source: usgs-iron-ore-2026
    where: World Mine Production and Reserves table, 2025e usable-ore column (world total 2,600,000 thousand t); shares computed by Space Mushroom from that table; Recycling line
documents:
  - title: Carpenter Technology Super Invar 32-5 data sheet (ASTM F1684, UNS K93500)
    type: datasheet
    url: https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Super%20Invar%2032-5.pdf
  - title: 'Hi-Temp Metals: Super Invar 32-5 technical data'
    type: datasheet
    url: https://www.hightempmetals.com/techdata/hitempSuperInvardata.php
  - title: Outer Planets Mission Television Subsystem Optics Study, final report, 28 July 1972 (NASA NTRS 19720025731)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19720025731/downloads/19720025731.pdf
    year: 1972
  - 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: Cobalt'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-cobalt.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Iron ore'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-ore.pdf
    year: 2026
  - title: 'PubChem: Cobalt (CID 104730)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/104730
    year: 2026
  - title: 'PubChem: Nickel (CID 935)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/935
    year: 2026
  - title: 'PubChem: Iron (CID 23925)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23925
    year: 2026
gaps:
  - 'Not found in the datasheet and supplier pages read in this run: melting point, Curie temperature, thermal conductivity and specific heat. Nothing was entered for them.'
  - Carpenter gives the mean CTE as 0.350 x 10-6 in/in/°F for -67 to 203 °F (-55 to 95 °C), with the exponent in the value cell. Under the exponent rule it was left out; the expansion value recorded is the Hi-Temp Metals figure of 0.63 ppm/°C from -55 to 95 °C.
  - Elastic modulus was left out. Hi-Temp Metals prints 144 under the unit x 10(6) MPa beside 21 under x 10(6) psi, which do not agree on the printed exponent. Carpenter prints 21.0 x 103 ksi with the exponent in the value. No modulus was entered rather than choose a unit.
  - No corrosion rate, humidity exposure or salt-spray result for Super Invar 32-5 was read. The corrosion entries rest on the heat-treatment oxidation statement, the forging soak statement and the plating statement.
  - 'The two typical analyses disagree: Hi-Temp Metals prints nickel 31.75 and cobalt 5.36 (weight units not printed), against Carpenter''s nominal 32.00 and 5.50 %. The Carpenter nominal values are used in the record and both are noted here.'
  - Carpenter's description gives the -67/203 °F (-55/95 °C) range as the one for which the alloy's thermal expansion is less than Invar 36's. Carpenter prints no Invar 36 value, so no Invar 36 number is recorded here.
  - 'Custom benchmark names not in property-canon.yaml: specific_gravity, martensite_start and hardness_rockwell_b (Rockwell B values 75 and 90 HRB, annealed and cold worked).'
  - The taxonomy has no controlled-expansion-alloy type, so this profile is filed under nickel-superalloys, as Invar 36 is. Super Invar is not a superalloy.
  - 'Cobalt''s critical-mineral status was not read: the USGS 2025 critical minerals list was not fetched in this run. The nickel critical-mineral entry cites the wording in the USGS nickel chapter.'
  - No vacuum outgassing, radiation, atomic-oxygen or thermal-vacuum data for Super Invar 32-5 were read. The only space source is the 1972 JPL/Itek study, a design report, which says Super-Invar was not used because its expansion properties were unstable over long periods of time.
  - Atomic weights are given for iron, nickel and cobalt only. Manganese, silicon and carbon appear in the type analysis without atomic weights.
  - No cryogenic expansion data below -55 °C were read.
  - No cost or lead-time data were read.
sources:
  carpenter-super-invar:
    title: 'Carpenter Technology: Super Invar 32-5 data sheet'
    id: Carpenter Technology data sheet, Super Invar 32-5 (ASTM F1684, UNS K93500)
    url: https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Super%20Invar%2032-5.pdf
    kind: datasheet
    license: Manufacturer datasheet, cited not reproduced
  hightempmetals-super-invar:
    title: 'Hi-Temp Metals: Super Invar 32-5 technical data'
    id: Hi-Temp Metals technical data page, Super Invar 32-5
    url: https://www.hightempmetals.com/techdata/hitempSuperInvardata.php
    kind: web
    license: Supplier page, cited not reproduced
  usgs-nickel-2026:
    title: 'Mineral Commodity Summaries 2026: Nickel'
    id: USGS MCS 2026, nickel
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: USGS public domain
  usgs-cobalt-2026:
    title: 'Mineral Commodity Summaries 2026: Cobalt'
    id: USGS MCS 2026, cobalt
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-cobalt.pdf
    year: 2026
    kind: report
    license: USGS public domain
  usgs-iron-ore-2026:
    title: 'Mineral Commodity Summaries 2026: Iron ore'
    id: USGS MCS 2026, iron ore
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-ore.pdf
    year: 2026
    kind: report
    license: USGS public domain
  ntrs-19720025731:
    title: Outer Planets Mission Television Subsystem Optics Study, final report, 28 July 1972
    id: NASA NTRS 19720025731 (Itek 72-9320-1, for JPL)
    url: https://ntrs.nasa.gov/api/citations/19720025731/downloads/19720025731.pdf
    year: 1972
    kind: report
    license: NASA NTRS public document
  pubchem-cobalt:
    title: 'PubChem: Cobalt (CID 104730), Safety and Hazards'
    id: PubChem CID 104730
    url: https://pubchem.ncbi.nlm.nih.gov/compound/104730
    year: 2026
    kind: database
    license: PubChem, U.S. National Library of Medicine
  pubchem-nickel:
    title: 'PubChem: Nickel (CID 935), Safety and Hazards'
    id: PubChem CID 935
    url: https://pubchem.ncbi.nlm.nih.gov/compound/935
    year: 2026
    kind: database
    license: PubChem, U.S. National Library of Medicine
  pubchem-iron:
    title: 'PubChem: Iron (CID 23925), molecular weight'
    id: PubChem CID 23925
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23925
    year: 2026
    kind: database
    license: PubChem, U.S. National Library of Medicine
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 16
  unreachable: 0
  caveats: 4
  note: |
    Values were read by an AI assistant on 2026-11-01 from the Carpenter Technology Super Invar 32-5 datasheet (PDF, converted with pdftotext), the Hi-Temp Metals technical data page, the USGS Mineral Commodity Summaries 2026 chapters for nickel, cobalt and iron ore (PDF), the 1972 JPL/Itek optics study (NASA NTRS PDF) and PubChem records. Caveats: the strengths and hardness are typical values of one manufacturer; the elastic modulus and the Carpenter expansion value are left out under the exponent rule; the specific gravity, martensite start and hardness names are custom; the space use comes from a 1972 design report rather than a test.
story:
  recipe:
    line: |
      Super Invar 32-5 is a magnetic, austenitic solid solution of iron, nickel and cobalt. Carpenter's nominal type analysis is 32.00 % nickel, 5.50 % cobalt, 0.40 % manganese, 0.25 % silicon and 0.02 % carbon, with iron as the balance. It is supplied as bar, billet, strip and wire.
    parts:
      - name: Iron
        symbol: Fe
        share_note: balance
        role: Balance of the alloy. Carpenter describes the alloy as magnetic and austenitic.
        source: pubchem-iron
        where: Elemental iron, PubChem CID 23925 (molecular weight read there, not entered)
      - name: Nickel
        symbol: Ni
        share_percent: 32
        share_note: wt%, nominal 32.00
        role: Carpenter says the alloy is designed to give minimum thermal expansion at room temperatures, and nickel is the main element in the type analysis.
        source: carpenter-super-invar
        where: Type analysis table, Nickel 32.00 %; elemental nickel, PubChem CID 935 (molecular weight read there, not entered)
      - name: Cobalt
        symbol: Co
        share_percent: 5.5
        share_note: wt%, nominal 5.50
        role: Named in the type analysis. The datasheet does not state its role.
        source: carpenter-super-invar
        where: Type analysis table, Cobalt 5.50 %; elemental cobalt, PubChem CID 104730 (molecular weight read there, not entered)
  risk_groups:
    - title: For people
      level: 1
      verdict: Cobalt and nickel are sensitisers; control dust
      lead: The alloy is mostly iron, but its cobalt and nickel are the health hazards, and machining produces dust and chips that carry them.
      points:
        - label: Skin
          line: PubChem's aggregated reports give H317 (may cause an allergic skin reaction) for more than 99.9 % of cobalt reports and for 99.9 % of nickel reports.
        - label: Breathing
          line: Cobalt is H334 (may cause allergy or asthma symptoms if inhaled) for more than 99.9 % of reports.
    - title: In service
      level: 2
      verdict: Stable only if heat-treated near finish size
      lead: Its low expansion depends on stress relief after fabrication, and the alloy oxidises during heat treatment.
      points:
        - label: Dimensional drift
          line: Fabricating stresses change the expansion behaviour, so Carpenter says to heat-treat at or as close to finish size as possible.
        - label: Oxidation
          line: Above about 1000 °F (538 °C) the alloy oxidises readily, so heat treatment needs a protective atmosphere.
    - title: In space
      level: 1
      verdict: Rejected for a 1972 telescope design
      lead: The space record here is a 1972 design study. No flight or test data for Super Invar 32-5 were read.
      points:
        - label: What the report says
          line: The 1972 JPL/Itek study did not use Super-Invar, because the expansion properties of the material were unstable over long periods of time.
        - label: What is missing
          line: No thermal-vacuum, outgassing or radiation test of Super Invar 32-5 was read.
  why: |
    Super Invar 32-5 is used where a metal must keep its length near room temperature. Hi-Temp Metals prints a mean coefficient of thermal expansion of 0.63 ppm/°C from -55 to 95 °C and a density of 8150 kg/m3. The cost is strength: the typical yield strength is 276 MPa and the typical tensile strength is 483 MPa, both in the annealed condition.
  uses:
    - where: Optical and laser systems
      line: Carpenter lists optical and laser systems among the applications of Super Invar 32-5 on its datasheet.
    - where: Semiconductor components and wave guide tubes
      line: Carpenter lists semiconductor components, wave guide tubes and other systems with low expansion glass or quartz assemblies.
  can_do:
    - label: Expansion
      benchmark: cte
      line: 0.63 ppm/°C from -55 to 95 °C, as a mean coefficient (Hi-Temp Metals).
    - label: Strength
      benchmark: yield_strength
      line: 276 MPa yield and 483 MPa tensile in the annealed condition (Carpenter typical values).
    - label: Ductility
      benchmark: elongation
      line: 40 % elongation in 2 in (50.8 mm) in the annealed condition (Carpenter typical value).
    - label: Density
      benchmark: density
      line: 8150 kg/m3 (Hi-Temp Metals).
    - label: Resistivity
      benchmark: electrical_resistivity
      line: 481.3 ohm-cir-mil/ft at 73 °F (23 °C) (Carpenter).
  compare: |
    Carpenter says the thermal expansion of Super Invar 32-5 is less than that of Invar 36 over -67/203 °F (-55/95 °C). The datasheet prints no Invar 36 value, so that comparison is qualitative here. Against other low-expansion metals, the figures to weigh are the 0.63 ppm/°C mean coefficient and the 276 MPa annealed yield strength for this grade.
  compare_rows:
    - label: Thermal expansion
      benchmark: cte
    - label: Density
      benchmark: density
    - label: Strength
      benchmark: yield_strength
  handling:
    - 'Heat-treat before final machining: heat to 1550 °F (843 °C) for 1 hour, water quench, stress-relieve at 600 °F (316 °C) for 1 hour, air cool, then age at 200 °F (93 °C) for 24 hours.'
    - Above about 1000 °F (538 °C), use a protective atmosphere such as vacuum, hydrogen, dissociated ammonia or inert gas.
    - Forge at 2000/2150 °F (1093/1177 °C) and do not soak long in the furnace, which can check the surface.
    - Degrease and clean machined parts soon after machining to remove residual sulfur, which can cause grain boundary embrittlement.
  good_for:
    - 'Parts that must hold a length near room temperature: mean coefficient 0.63 ppm/°C from -55 to 95 °C.'
    - Optical and laser systems, semiconductor components and wave guide tubes, per Carpenter's applications list.
    - Assemblies that must match low expansion glass or quartz, per Carpenter.
  watch_out:
    - 'Long-term expansion drift: the 1972 JPL/Itek study rejected Super-Invar for this reason.'
    - Cold work changes the expansion, so heat-treat parts at or as close to finish size as possible.
    - No corrosion rate or humidity test was read; the datasheet lists plating and zinc coating as the usual finishes.
  verdict: |
    Super Invar 32-5 suits parts that must hold a length near room temperature, where Carpenter says its expansion is lower than Invar 36's. Design with its 0.63 ppm/°C mean coefficient and 276 MPa annealed yield strength, but note that the 1972 JPL study rejected it for long-term expansion stability, and that no corrosion rate was found.