spore: profile
id: constantan
spore_version: 0.2
family: resistance-and-thermocouple-alloys
name: Constantan
abbreviation: CuNi
role: precision resistance alloy and thermocouple leg
category: metals
type: copper-alloys
summary: |
  Constantan is a copper-nickel alloy of about 55 % copper and 45 % nickel, sold as DIN 2.0842, UNS C72150 and CuNi44Mn1. Its electrical resistance stays nearly constant over a wide temperature range, which is why it is used in strain gauges, precision and shunt resistors, and as one leg of thermocouples. Matthey gives a density of 8.9 g/cm3, a thermal conductivity of 21.2 W/(m·K) at 20 °C and a temperature coefficient of resistance of -80 to +40 ppm/K. Soft annealed strip has a tensile strength of 360 to 460 MPa and at least 25 % elongation, and the maker rates the alloy to 600 °C.
best_for: Precision resistors, strain gauges and thermocouple legs that need a resistance which stays nearly constant with temperature, up to about 600 °C
weakest_at: 'Conduction and heat flow: resistivity of 52 µΩ·cm (Goodfellow) and thermal conductivity of 21.2 W/(m·K) (Matthey) make it a resistor alloy, not a conductor. Nickel content also brings a skin-sensitisation hazard (H317 on the nickel SDS).'
identity:
  formula: Cu-Ni alloy, nominal 55 % Cu and 45 % Ni, with 0.50 to 2.00 % Mn (Matthey CuNi44Mn1); Cu balance, Ni 43 to 45 %, Mn 0.7 to 1.3 %, Fe up to 1 % (BGH CuniTHERM 44)
  source: matthey-cunimn44
  where: 'Chemical composition table, row Cu Balance, Ni 43.0 - 45.0, Mn 0.50 - 2.00 (weight %). The BGH sheet prints the same nominal split: Ni min 43 and max 45, Cu balance.'
  designations:
    - system: UNS
      code: C72150
      source: bgh-cunitherm44
      where: Material Designation table, row C72150, label UNS
    - system: EN
      code: '2.0842'
      source: bgh-cunitherm44
      where: Material Designation table, row 2.0842, label DIN; Standards line DIN 17471
    - system: EN name
      code: CuNi44Mn1
      source: matthey-cunimn44
      where: Title block, designation CuNi44Mn1
    - system: Trade name
      code: Constantan
      source: bgh-cunitherm44
      where: 'Properties paragraph: also known under the brand name constantan'
tags:
  environments: []
  applications:
    - electronics-and-chips
    - thermal-control
    - structures
properties:
  - benchmark: density
    label: Density, CuNi44Mn1 strip
    value: 8.9
    unit: g/cm3
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Density
  - benchmark: density
    label: Density, annealed wire 0.15 mm
    value: 8.9
    unit: g/cm3
    scope: material
    conditions:
      form: annealed spooled wire, diameter 0.15 mm (Goodfellow SKU 1000058743)
      temperature: not stated
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Physical Properties table, row Density
  - benchmark: melting_point
    label: Melting point range, CuNi44Mn1
    value: 1230
    value_high: 1290
    bound: range
    unit: °C
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      pressure: not stated
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Melting point
  - benchmark: melting_point
    label: Melting point range, annealed wire
    value: 1225
    value_high: 1300
    bound: range
    unit: °C
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      pressure: not stated
    method: Range printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Thermal Properties table, row Melting point
  - benchmark: electrical_resistivity
    label: Electrical resistivity, annealed wire 0.15 mm
    value: 52
    unit: µΩ·cm
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow SKU 1000058743)
      temperature: not stated
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Electrical Properties table, row Electrical resistivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 20 °C, CuNi44Mn1 strip
    value: 21.2
    unit: W/(m·K)
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temperature: 20 °C
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Thermal conductivity at 20°C
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 23 °C, annealed wire
    value: 19.5
    unit: W/(m·K)
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      temperature: 23 °C
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Thermal Properties table, row Thermal conductivity
  - benchmark: cte
    label: Coefficient of thermal expansion, 20 to 300 °C, CuNi44Mn1 strip
    value: 14.5
    unit: ppm/K
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temperature: 20 to 300 °C
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Linear dilatation coefficient (20-300 ºC)
  - benchmark: cte
    label: Coefficient of thermal expansion, 20 to 100 °C, annealed wire
    value: 14.9
    unit: ppm/K
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      temperature: 20 to 100 °C
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Thermal Properties table, row Coefficient of thermal expansion
  - benchmark: specific_heat
    label: Specific heat capacity at 20 °C, CuNi44Mn1 strip
    value: 0.41
    unit: kJ/(kg·K)
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temperature: 20 °C
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Thermal capacity (Cp) at 20ºC
  - benchmark: elastic_modulus
    label: Modulus of elasticity, CuNi44Mn1 strip
    value: 165
    unit: kN/mm2
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temperature: not stated
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Modulus of elasticity
  - benchmark: elastic_modulus
    label: Modulus of elasticity, annealed wire 0.15 mm
    value: 162
    unit: GPa
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      temperature: not stated
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Mechanical Properties table, row Modulus of elasticity
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, soft annealed strip (R360, H90)
    value: 360
    value_high: 460
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temper: soft annealed, R360 / H90
      product_form: strip
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Mechanical properties of strips, row R360 H90 soft annealed, column Rm (N/mm2)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, half-hard strip (R500, H150)
    value: 500
    value_high: 700
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temper: 1/2 hard, R500 / H150
      product_form: strip
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Mechanical properties of strips, row R500 H150 1/2 hard, column Rm (N/mm2)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, hard strip (R740, H230), minimum
    value: 740
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temper: hard, R740 / H230
      product_form: strip
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Mechanical properties of strips, row R740 H230 hard, column Rm (N/mm2)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, annealed wire 0.15 mm
    value: 400
    value_high: 590
    bound: range
    unit: MPa
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      temper: annealed
    method: Range printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Mechanical Properties table, row Tensile strength
  - benchmark: elongation
    label: Elongation, soft annealed strip (R360, H90)
    value: 25
    bound: lower
    unit: '%'
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temper: soft annealed, R360 / H90
      gauge_length: A50mm
    method: Minimum value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Mechanical properties of strips, row R360 H90 soft annealed, column A50mm (%)
  - benchmark: elongation
    label: Elongation at break, annealed wire 0.15 mm
    value: 45
    unit: '%'
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      temper: annealed
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Mechanical Properties table, row Elongation at break
  - benchmark: max_service_temp
    label: Maximum application temperature, CuNi44Mn1
    value: 600
    unit: °C
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      basis: maximum application temperature, as stated by the maker
    method: Value printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Main technical properties and features, last sentence; also Physical properties table, row Maximum application temperature
  - benchmark: max_service_temp
    label: Maximum use temperature in air, annealed wire
    value: 500
    unit: °C
    scope: material
    conditions:
      form: annealed spooled wire 0.15 mm (Goodfellow)
      atmosphere: air
    method: Value printed in a supplier product page
    status: ground
    source: goodfellow-wire
    where: Thermal Properties table, row Maximum use temperature in air
  - benchmark: temperature_coefficient_of_resistance
    label: Temperature coefficient of electrical resistance, CuNi44Mn1
    value: -80
    value_high: 40
    bound: range
    unit: ppm/K
    scope: material
    conditions:
      grade: CuNi44Mn1 (Matthey)
      temperature: 20 to 105 °C
    method: Range printed in a manufacturer datasheet
    status: ground
    source: matthey-cunimn44
    where: Physical properties table, row Temperature coefficient of electrical resistance (20-105 °C)
  - benchmark: thermoelectric_emf_vs_copper
    label: Thermoelectric emf compared with copper
    value: -40
    unit: µV/K
    scope: material
    conditions:
      reference: emf compared with copper (Cu)
      temperature: not stated in the printed table
    method: Value printed in a manufacturer datasheet (DIN 17471 physical properties)
    status: ground
    source: bgh-cunitherm44
    where: Physical Properties table acc. to DIN 17471, row Thermoelectric emf compared to Cu
corrosion:
  - environment: Oxygen-containing and oxidising sulphurous gases at high temperature
    headline: The alloy is scale-resistant and resists oxidising sulphurous gases up to 600 °C.
    effect: BGH says the material is scale-resistant and resistant up to 600 °C to oxygen-containing and oxidising sulphurous gases, and to carburisation, among others. The sheet gives no test data or rate.
    rating: low
    conditions:
      temperature: up to 600 °C
      basis: manufacturer statement, no test data printed
    source: bgh-cunitherm44
    where: Description paragraph under Properties
  - environment: General corrosive media at ambient temperature
    headline: Good corrosion resistance, malleability and ductility, and an adherent oxide coating can be applied to strip.
    effect: Matthey says CuNi44Mn1 has good corrosion resistance, good malleability and ductility, and that an adherent oxide coating with excellent electrical insulation can be applied to the strip surface. No corrosion rate or immersion test is printed.
    rating: low
    conditions:
      basis: manufacturer statement, no test data printed
    source: matthey-cunimn44
    where: Main technical properties and features
risks:
  hazards:
    - text: Nickel is about 45 % of the alloy. The nickel wire safety data sheet (NextSDS, CAS 7440-02-0, EC 231-111-4) lists H317 May cause an allergic skin reaction, H351 Suspected of causing cancer and H372 Causes damage to the lung, the kidneys and the liver through prolonged or repeated exposure, with signal word danger. That is the nickel metal classification, not a constantan SDS, and the constantan SDS was not opened.
      ghs:
        - H317
        - H351
        - H372
      source: nextsds-ni
      where: Hazard Classifications and Hazard Statements section of the nickel wire SDS page
    - text: Goodfellow's product page for constantan wire (0.15 mm) shows a health hazard label reading Serious health hazard. The constantan SDS is a UK document behind a download link and was not opened, so no H-codes for the alloy itself are recorded.
      ghs: []
      source: goodfellow-wire
      where: Product details block, label Health hazard
  failure_risks:
    - mode: Use above the maximum application temperature
      trigger: Operation above 600 °C (Matthey maximum application temperature) or above 500 °C in air for annealed wire (Goodfellow)
      consequence: Neither supplier prints property data above these limits, so the alloy is outside its rated range. The sources give no failure data for that case.
      severity: moderate
      source: matthey-cunimn44
      where: Main technical properties and features (maximum application temperature 600 °C); Goodfellow product page for the 500 °C air limit
    - mode: Wrong temper for the load
      trigger: Soft annealed strip specified where hard strip is meant, or the reverse
      consequence: Minimum tensile strength falls from 740 MPa in the hard temper to 360 to 460 MPa when soft annealed, so the temper sets the strength of the part.
      severity: low
      source: matthey-cunimn44
      where: Mechanical properties of strips, rows R360 H90, R500 H150 and R740 H230
  side_effects:
    - text: The alloy is about 45 % nickel, so its cost follows nickel supply and price. The USGS says the 2025 average LME nickel cash price fell by an estimated 11 % from 2024, and that the global primary nickel market has been in surplus since 2022.
      affects: Cost of the alloy
      source: usgs-ni-2026
      where: Events, Trends, and Issues section
  handling:
    - text: Specify the temper when ordering. Soft annealed strip has 360 to 460 MPa tensile strength and hard strip 740 MPa minimum (Matthey), and the Goodfellow wire is supplied annealed.
      source: matthey-cunimn44
      where: Mechanical properties of strips table
    - text: The nickel wire SDS lists skin sensitisation (H317) for the nickel component, so the constantan SDS from the supplier should be checked before handling the wire.
      source: nextsds-ni
      where: Hazard Statements section
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Precision and shunt resistors, and measuring resistors
    example: Matthey lists shunt resistors for ammeters and electrical resistors for measurement among typical uses. BGH lists precision and measuring resistors. Its near-constant resistivity is the reason for the choice.
    source: matthey-cunimn44
    where: Typical uses section; also BGH Typical Applications list
  - application: thermal-control
    device: Thermocouple leg (copper-nickel or iron pairing) for temperature measurement
    example: Matthey says the very high EMF of CuNi44Mn1 suits thermocouples combined with other metals. BGH gives a thermoelectric emf of -40 µV/K against copper. The NIST-based Type T table pairs copper with copper-nickel over -200 to 350 °C in its thermocouple grade.
    source: mst-typet
    where: Type T reference table, title block (Copper vs. Copper-Nickel; maximum temperature range, thermocouple grade); Matthey Main technical properties
  - application: structures
    device: Strain gauge grids and multipurpose instrumentation cable
    example: Matthey and Goodfellow both list strain gauges as a use. AEC-NASA Tech Brief 67-10046 (1967, Space Nuclear Propulsion Office) describes a cable with a constantan conductor that forms the negative leg of a copper/constantan thermocouple, so a strain gauge's own temperature can be measured. This is a development record, not a flight record.
    source: ntrs-1967
    where: Brief 67-10046, The problem and How it's done sections; Matthey Typical uses
  - application: thermal-control
    device: Heating wires, cables and heating mats up to 600 °C
    example: BGH lists heating wires and cables and heating mats, for low-temperature heating elements with application temperatures up to 600 °C.
    source: bgh-cunitherm44
    where: Application Area and Typical Applications, Physical Properties paragraph
supply:
  - subject: Copper (about 55 % of the alloy), mine production 2025e
    producers:
      - country: Chile
        share_percent: 23
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 13.9
        year: 2025
      - country: Peru
        share_percent: 11.7
        year: 2025
      - country: China
        share_percent: 7.8
        year: 2025
      - country: Russia
        share_percent: 5.7
        year: 2025
    critical_lists:
      - list: U.S. Final 2025 List of Critical Minerals (copper added, per the USGS Mineral Commodity Summaries 2026)
        listed: true
    recycling: 'USGS: old scrap provided about 30 % of the U.S. copper supply in 2025, and brass and wire-rod mills took about 80 % of the copper recovered from scrap.'
    substitutes:
      - 'USGS: aluminium substitutes for copper in electrical equipment and power cable.'
    source: usgs-cu-2026
    where: World Mine and Refinery Production table, mine production 2025e (world total 23,000 thousand t). Shares calculated from the printed country values 5,300, 3,200, 2,700, 1,800 and 1,300 over 23,000. Critical list in the 2025 list paragraph. Recycling and Substitutes sections.
  - subject: Nickel (about 45 % of the alloy), mine production 2025e
    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
    recycling: 'USGS: nickel recovered from scrap accounted for about 60 % of U.S. apparent consumption in 2025. The last U.S. primary nickel refinery stopped operating in 1985.'
    substitutes:
      - 'USGS: titanium alloys can substitute for nickel or nickel-base alloys in corrosive environments; low-nickel and duplex stainless steels substitute for austenitic grades.'
    source: usgs-ni-2026
    where: World Mine Production and Reserves table, 2025e column (world total 3,900,000 t). Shares calculated from the printed values 2,600,000, 270,000, 200,000 and 140,000 (twice) over 3,900,000. Recycling and Substitutes paragraphs.
documents:
  - title: BGH CuniTHERM 44 (constantan) premium resistance alloy datasheet, Rev. 1
    type: datasheet
    url: https://bgh.de/media/84/0c/4d/1775720815/BGH_CuniTHERM%2044_en.pdf
  - title: Lamineries Matthey, Constantan CuNi44Mn1 technical datasheet (v22E)
    type: datasheet
    url: https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/EN/CuNi44Mn1_v22E.pdf
    year: 2022
  - title: Goodfellow, Constantan spooled wire 0.15 mm (SKU 1000058743), product and properties page
    type: datasheet
    url: https://www.goodfellow.com/uk/constantan-spooled-wire-1000058743
  - title: Goodfellow, Constantan resistance alloy wire, material information
    type: report
    url: https://www.goodfellow.com/usa/resources/constantan-resistance-alloy-wire-material-information/
    year: 2024
  - title: 'USGS Mineral Commodity Summaries 2026: Copper'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
  - title: NIST Monograph 175 revised to ITS-90, Thermocouple Reference Tables, Type T (copy hosted by Missouri S&T)
    type: database
    url: https://web.mst.edu/cottrell/ME240/Resources/Temperature/Type%20T%20TC%20Table.pdf
  - title: NextSDS, Nickel wire safety data sheet, CAS 7440-02-0, hazard classification
    type: sds
    url: https://nextsds.com/sds/en/281331501257788/nickel-wire
  - title: AEC-NASA Tech Brief 67-10046, Multipurpose Instrumentation Cable Provides Integral Thermocouple Circuit (March 1967)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19670000046/downloads/19670000046.pdf
    year: 1967
gaps:
  - 'Electrical resistivity 0.49 Ω mm²/m at 20 °C from the BGH sheet is not entered: the sheet prints it with a decimal comma (0,49), which the value check cannot match. The Goodfellow value of 52 µΩ·cm is entered instead.'
  - Matthey prints electrical resistivity as 49 with the unit cm (the micro sign is lost in the PDF text), so the unit is not confirmed and the value is not entered. Goodfellow's material information page gives 49 × 10⁻⁸ Ω·m at 20 °C in a form the unit parser cannot take, so it is not entered either.
  - The BGH sheet prints its melting temperature (1280), thermal expansion (13.5 and 15) and temperature-coefficient range under a column header in °F. Those values are not entered because the unit is not confirmed. The BGH sheet's decimal-comma density (8,9), specific heat (0,41) and thermal conductivity (23,0) are also not entered, for the same comma reason as the resistivity.
  - 'Yield strength: no source read in this run gives a yield value for constantan, so only tensile strength and elongation are entered.'
  - 'Hardness: Goodfellow gives 100 to 300 HB (Brinell) and Matthey gives 90 to 135 HV (soft) and 150 to 220 HV (half hard). Neither is entered because no canonical hardness name exists in the property list.'
  - Temperature coefficient of resistance and thermoelectric emf are entered under names that are not in the canonical property list (temperature_coefficient_of_resistance, thermoelectric_emf_vs_copper). They need adding to the list.
  - 'Designations: BGH also prints UNS N04401 for the same product; it is not entered because it is a different UNS number from C72150 and the sheet does not call the two the same grade. Wikipedia gives the trade names Eureka, Advance and Ferry; it was not used for designations, because the brief limits Wikipedia to composition and history.'
  - 'Constantan SDS: the supplier SDS (Goodfellow, UK) was not opened, so no H-codes for the alloy are recorded. The hazard entries use the nickel metal SDS and the supplier''s health hazard label.'
  - 'Spacecraft, rocket and satellite use: no flight record of constantan was found in a source read in this run. The 1967 AEC-NASA Tech Brief describes a Space Nuclear Propulsion Office instrumentation cable, which is a development record. A 1977 NASA surface-thermocouple brief was seen in a search result only and not opened.'
  - 'Type J (iron-constantan): the pairing is not confirmed from a source read in this run. The ISA MC96.1 preview and the Omega table were not readable in this run.'
  - 'Vacuum and space environment: no outgassing, atomic-oxygen, radiation or cold-welding data for constantan was found.'
  - Supply shares are calculated from printed USGS values, not printed as percentages in the sources.
  - 'Fatigue, creep and drift: BGH and Matthey give no drift or fatigue data. Wikipedia reports drift above 65 °C in strain gauge use, but it was not used for property or failure values under the brief.'
sources:
  bgh-cunitherm44:
    title: BGH CuniTHERM 44, premium resistance alloy datasheet (Rev. 1, English)
    url: https://bgh.de/media/84/0c/4d/1775720815/BGH_CuniTHERM%2044_en.pdf
    kind: datasheet
    license: Manufacturer datasheet, unbinding first orientation (cited, not reproduced)
  matthey-cunimn44:
    title: Lamineries Matthey, Constantan CuNi44Mn1 technical datasheet (v22E, 2022)
    url: https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/EN/CuNi44Mn1_v22E.pdf
    year: 2022
    kind: datasheet
    license: Manufacturer datasheet, informative only (cited, not reproduced)
  goodfellow-wire:
    title: Goodfellow, Constantan spooled wire 0.15 mm (SKU 1000058743), product page with material properties
    url: https://www.goodfellow.com/uk/constantan-spooled-wire-1000058743
    kind: datasheet
    license: Supplier product page (cited, not reproduced)
  goodfellow-info:
    title: Goodfellow, Constantan resistance alloy wire, material information (January 2024)
    url: https://www.goodfellow.com/usa/resources/constantan-resistance-alloy-wire-material-information/
    year: 2024
    kind: web
    license: Supplier web page (cited, not reproduced)
  usgs-cu-2026:
    title: Mineral Commodity Summaries 2026, Copper
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-ni-2026:
    title: Mineral Commodity Summaries 2026, Nickel
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  mst-typet:
    title: NIST Monograph 175 revised to ITS-90, Thermocouple Reference Tables, Type T (copy hosted by Missouri S&T)
    url: https://web.mst.edu/cottrell/ME240/Resources/Temperature/Type%20T%20TC%20Table.pdf
    kind: database
    license: US government reference table (cited, not reproduced)
  nextsds-ni:
    title: NextSDS, Nickel wire safety data sheet, CAS 7440-02-0, hazard classification
    url: https://nextsds.com/sds/en/281331501257788/nickel-wire
    kind: datasheet
    license: SDS summary page (cited, not reproduced)
  ntrs-1967:
    title: AEC-NASA Tech Brief 67-10046, Multipurpose Instrumentation Cable Provides Integral Thermocouple Circuit (March 1967)
    url: https://ntrs.nasa.gov/api/citations/19670000046/downloads/19670000046.pdf
    year: 1967
    kind: report
    license: public domain (NASA)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 23
  unreachable: 2
  caveats: 6
  note: 'Values were read by an AI assistant on 2026-10-26 from the datasheets and product page named in each entry (PDFs extracted to text). Unreachable or unconfirmed: the constantan SDS from the supplier, and the Omega and ISA Type J pages. Caveats: the BGH sheet uses a [°F] column header with values that look like °C, so those rows are left out; the Goodfellow wire values are for one 0.15 mm annealed product; Matthey strip tempers differ from wire; the nickel hazard classification is for the nickel metal, not the alloy; the space use is a 1967 development brief.'
story:
  risk_groups:
    - title: For people
      lead: The hazard of constantan comes from its nickel. The opened sources classify nickel metal, not the alloy itself, and the supplier's own SDS was not read.
      level: 1
      verdict: Nickel classification
      points:
        - label: Nickel in the alloy
          line: The nickel wire SDS lists H317 (allergic skin reaction), H351 (suspected of causing cancer) and H372 (damage to lungs, kidneys and liver through prolonged exposure). Nickel is about 45 % of constantan.
        - label: Supplier label
          line: Goodfellow's constantan wire page shows a health hazard label reading Serious health hazard. The full SDS was not opened.
    - title: If it fails
      lead: The sources give rating and temper limits, but no failure data for the alloy beyond them.
      points:
        - label: Above 600 °C
          line: Matthey gives 600 °C as the maximum application temperature, and Goodfellow gives 500 °C in air for annealed wire. Above those limits no property data are printed.
        - label: Wrong temper
          line: Hard strip has at least 740 MPa tensile strength, against 360 to 460 MPa when soft annealed.
    - title: Handling and storage
      points:
        - label: Choose the temper
          line: Name the temper on the order. Matthey gives soft (H90), half-hard (H150) and hard (H230) strip with different strengths.
        - label: Check the SDS
          line: Read the supplier's SDS before handling, since the nickel component carries a skin-sensitisation classification.
  why: Constantan is a copper-nickel alloy of about 55 % copper and 45 % nickel. Its electrical resistance stays nearly constant over a wide temperature range, so it is used where a resistor must not drift with temperature. Matthey gives a temperature coefficient of resistance of -80 to +40 ppm/K over 20 to 105 °C. The same alloy has a thermoelectric emf against copper of -40 µV/K, so it is also used as one leg of a thermocouple. It is a strain gauge alloy too, with 162 GPa modulus and 45 % elongation in annealed wire.
  uses:
    - where: Resistors and gauges
      line: Matthey lists shunt resistors for ammeters, measuring resistors and strain gauges among its typical uses. BGH lists precision and measuring resistors. Goodfellow describes the wire as used in strain gauges, resistance thermometers and precision shunt resistors.
    - where: Thermocouples
      line: Matthey says the alloy's very high emf suits thermocouples combined with other metals. A NIST-based Type T table pairs copper with copper-nickel over -200 to 350 °C in its thermocouple grade.
    - where: Heating elements
      line: BGH lists heating wires and cables and heating mats, for low-temperature heating elements with application temperatures up to 600 °C.
    - where: Aerospace instrumentation
      line: A 1967 AEC-NASA Tech Brief describes a multipurpose cable with a constantan conductor that doubles as a thermocouple leg, so a strain gauge's temperature can be measured without a second thermocouple. It is a development record, not a flight record.
  can_do:
    - label: Stay constant
      value: '-80 to +40 ppm/K'
      benchmark: temperature_coefficient_of_resistance
      line: Matthey gives a temperature coefficient of electrical resistance of -80 to +40 ppm/K over 20 to 105 °C.
    - label: Carry heat
      value: 21.2 W/(m·K)
      benchmark: thermal_conductivity
      line: Matthey gives a thermal conductivity of 21.2 W/(m·K) at 20 °C. Goodfellow gives 19.5 W/(m·K) at 23 °C for annealed wire.
    - label: Stay in the heat
      value: 600 °C
      benchmark: max_service_temp
      line: Matthey gives 600 °C as the maximum application temperature. BGH says the alloy is scale-resistant up to 600 °C in oxidising sulphurous gases.
    - label: Weight
      value: 8.9 g/cm3
      benchmark: density
      line: Density is 8.9 g/cm3 in both the Matthey strip sheet and the Goodfellow wire page.
    - label: Strength by temper
      value: 360 to 740 MPa
      benchmark: ultimate_tensile_strength
      line: Tensile strength is 360 to 460 MPa in soft annealed strip, 500 to 700 MPa in half-hard strip and at least 740 MPa in hard strip (Matthey).
  compare: 'Two suppliers give different thermal conductivities for the same nominal alloy: 21.2 W/(m·K) at 20 °C from Matthey and 19.5 W/(m·K) at 23 °C from Goodfellow for annealed wire. Matthey''s strip tempers span tensile strengths from 360 to 740 MPa, so the temper decides the strength. The table rows are examples from these two datasheets, not a ranking.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Maximum temperature
      benchmark: max_service_temp
  handling:
    - Name the temper on the order, because strength runs from 360 to 460 MPa soft to 740 MPa minimum hard.
    - Keep the alloy at or below 600 °C in use, the maximum application temperature given by Matthey.
    - Read the supplier SDS before handling, since the nickel component carries H317, H351 and H372 in its own SDS.
  good_for:
    - Precision resistance with a temperature coefficient of -80 to +40 ppm/K (Matthey).
    - Strain gauges and thermocouple legs, with a 162 GPa modulus and 45 % elongation in annealed wire (Goodfellow).
    - Use up to 600 °C in oxidising gases, as stated by BGH and Matthey.
  watch_out:
    - 'Nickel content: the nickel component is classified H317, H351 and H372 in its own SDS.'
    - 'Conduction: resistivity is 52 µΩ·cm (Goodfellow), so the alloy is a resistor, not a conductor.'
    - 'Temper: strength depends strongly on temper, from 360 to 460 MPa soft to 740 MPa minimum hard.'
    - 'Supply: about 67 % of 2025 world nickel mine output came from Indonesia (USGS).'
    - 'Space: no flight record of constantan was found in the sources read; the 1967 NASA brief is a development record.'
  verdict: Constantan is a copper-nickel resistance alloy whose resistance barely changes with temperature, with -80 to +40 ppm/K from Matthey. It also works as a thermocouple leg and a strain gauge alloy, rated to 600 °C. Its nickel content carries a hazard classification, the datasheets give no failure data above the rated limits, and no flight record in a space source was found.
  recipe:
    line: Constantan is a copper-nickel alloy (Cu-Ni) with a face-centred cubic crystal structure, typically 55 % copper and 45 % nickel (Goodfellow material information). Matthey's CuNi44Mn1 adds 0.50 to 2.00 % manganese and up to 0.50 % iron (Matthey composition table). It is supplied as wire, strip and foil.
    parts:
      - name: Copper
        symbol: Cu
        share: about 55 wt% (balance in Matthey's table)
        role: Base metal of the alloy. Copper sets the low-cost matrix that the nickel is dissolved in.
      - name: Nickel
        symbol: Ni
        share: 43.0 to 45.0 wt% (Matthey)
        role: Main alloying element. It gives the alloy its near-constant resistivity with temperature.
      - name: Manganese
        symbol: Mn
        share: 0.50 to 2.00 wt% (Matthey); 0.7 to 1.3 wt% (BGH)
        role: Minor addition in the CuNi44Mn1 grade.