{
  "spore": "profile",
  "id": "invar-36",
  "spore_version": "0.2",
  "family": "nickel-alloys",
  "name": "Invar 36",
  "abbreviation": "FeNi36",
  "role": "low-expansion structural alloy",
  "category": "metals",
  "type": "nickel-superalloys",
  "summary": "Invar 36 is an iron-nickel alloy with 36 % nickel whose thermal expansion nearly cancels near room temperature: 1.3 ppm/K from room temperature to 93 °C, against roughly 11 to 15 ppm/K for ordinary steel. That is why it is used for the structures that hold optical elements at a fixed spacing in telescopes and instruments. It is a soft metal (276 MPa yield in the annealed condition), loses corrosion resistance in humid air, and drifts dimensionally unless it is stress-relieved before final machining.\n",
  "best_for": "Holding a dimension across temperature changes: 1.3 ppm/K near room temperature, and 1.8 ppm/K between -240 and -18 °C",
  "weakest_at": "Humid air, where Matthey says its corrosion resistance falls; and dimensional drift from cold work unless it is heat-treated before final machining",
  "identity": {
    "formula": "Fe-36Ni (FeNi36, 64FeNi): iron with 36.00 wt% nickel nominal (range 35.0-37.0), manganese 0.35 (maximum 0.60), silicon 0.20 (maximum 0.40), carbon 0.02 (maximum 0.15), iron balance; UNS K93600, K93601 and K93603",
    "crystal_system": "face-centred cubic",
    "designations": [],
    "source": "matthey-feni36",
    "where": "Chemical composition table (Fe balance, Ni 35.0-37.0, Si <= 0.40, Mn <= 0.60, C <= 0.15); the nominal 36.00 / 0.35 / 0.20 / 0.02 values are Carpenter's type analysis; UNS numbers are printed by Carpenter (K93601, K93603), Nicofe (K93603) and Matthey (approximately K93600); the face-centred-cubic lattice is stated in Matthey's Technische Hauptmerkmale"
  },
  "tags": {
    "environments": [
      "deep-space"
    ],
    "stresses": [
      "extreme-cold",
      "thermal-cycling",
      "vibration"
    ],
    "applications": [
      "optics-and-cameras",
      "electronics-and-chips",
      "cryogenic-fuel"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "value": 8.05,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "form": "wrought bar and strip",
        "temperature": "not stated"
      },
      "method": "Value printed in a supplier datasheet",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "PHYSICAL PROPERTIES table, row Density",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "value": 8.13,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "form": "cold-rolled strip and foil",
        "temperature": "not stated",
        "note": "higher than the 8.05 printed by Nicofe and by Carpenter; not reconciled in the sources"
      },
      "method": "Value printed in a producer datasheet",
      "status": "ground",
      "source": "matthey-feni36",
      "where": "Physikalische Eigenschaften, row Dichte (spezifisches Gewicht)",
      "source_detail": {
        "title": "Lamineries Matthey: Invar FeNi36 datasheet",
        "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
        "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
        "kind": "datasheet",
        "license": "Producer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "value": 1.3,
      "bound": "exact",
      "unit": "ppm/K",
      "scope": "material",
      "conditions": {
        "temperature_range": "21 to 93 °C (70 to 200 °F)",
        "unit_in_source": "1.30 x 10^-6 cm/cm/°C in the metric column; 0.72 x 10^-6 in/in/°F in the English column"
      },
      "method": "Mean coefficient of thermal expansion from the manufacturer's table; the metric column was copied and the English column is kept in unit_in_source",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Physical properties, row MEAN COEFFICIENT OF THERMAL EXPANSION, 200 °F (93 °C) line",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "value": 2.11,
      "bound": "exact",
      "unit": "ppm/K",
      "scope": "material",
      "conditions": {
        "temperature_range": "21 to 149 °C (70 to 300 °F)",
        "unit_in_source": "2.11 x 10^-6 cm/cm/°C; 1.17 x 10^-6 in/in/°F"
      },
      "method": "Mean coefficient of thermal expansion from the manufacturer's table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Physical properties, row MEAN COEFFICIENT OF THERMAL EXPANSION, 300 °F (149 °C) line",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "value": 4.18,
      "bound": "exact",
      "unit": "ppm/K",
      "scope": "material",
      "conditions": {
        "temperature_range": "21 to 260 °C (70 to 500 °F)",
        "unit_in_source": "4.18 x 10^-6 cm/cm/°C; 2.32 x 10^-6 in/in/°F"
      },
      "method": "Mean coefficient of thermal expansion from the manufacturer's table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Physical properties, row MEAN COEFFICIENT OF THERMAL EXPANSION, 500 °F (260 °C) line",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "value": 1.18,
      "bound": "exact",
      "unit": "ppm/°C",
      "scope": "material",
      "conditions": {
        "temperature_range": "30 to 100 °C",
        "unit_in_source": "1.18 (ppm/°C)"
      },
      "method": "Value printed in the supplier's linear-expansion table",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "LINEAR COEFFICIENT OF PHYSICAL THERMAL EXPANSION table, 30-100 °C line",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "value": 4.92,
      "bound": "exact",
      "unit": "ppm/°C",
      "scope": "material",
      "conditions": {
        "temperature_range": "30 to 300 °C",
        "unit_in_source": "4.92 (ppm/°C)"
      },
      "method": "Value printed in the supplier's linear-expansion table",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "LINEAR COEFFICIENT OF PHYSICAL THERMAL EXPANSION table, 30-300 °C line",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "value": 1.8,
      "bound": "exact",
      "unit": "ppm/°C",
      "scope": "material",
      "conditions": {
        "temperature_range": "-240 to -18 °C",
        "unit_in_source": "1.8 (10^-6/ºC)",
        "note": "the only cryogenic entry read; no value below -240 °C"
      },
      "method": "Value printed in the producer's physical-properties table",
      "status": "ground",
      "source": "matthey-feni36",
      "where": "Physikalische Eigenschaften, row Wärme-Ausdehnungskoeffizient lin.",
      "source_detail": {
        "title": "Lamineries Matthey: Invar FeNi36 datasheet",
        "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
        "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
        "kind": "datasheet",
        "license": "Producer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "value": 1427,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "melting range, printed as 2600 °F (1427 °C); not a single melting point"
      },
      "method": "Value printed in the manufacturer's physical-properties table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Physical properties, row MELTING RANGE",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "curie_temperature",
      "value": 279,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "printed_as": "535 °F / 279 °C"
      },
      "method": "Value printed in the manufacturer's physical-properties table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Physical properties, row CURIE TEMPERATURE",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "specific_heat",
      "value": 515,
      "bound": "exact",
      "unit": "J/(kg·K)",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C"
      },
      "method": "Value printed in the producer's physical-properties table",
      "status": "ground",
      "source": "matthey-feni36",
      "where": "Physikalische Eigenschaften, row Spezifische Wärme bei 20°C",
      "source_detail": {
        "title": "Lamineries Matthey: Invar FeNi36 datasheet",
        "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
        "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
        "kind": "datasheet",
        "license": "Producer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "value": 72.85,
      "bound": "exact",
      "unit": "Btu·in/(hr·ft²·°F)",
      "scope": "material",
      "conditions": {
        "temperature": "not stated",
        "unit_in_source": "72.85 Btu-in/hr/ft2/°F, equal to about 10.5 W/(m·K)"
      },
      "method": "Value printed in the manufacturer's physical-properties table; the importer converts the printed unit",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Physical properties, row THERMAL CONDUCTIVITY",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "value": 10.5,
      "bound": "exact",
      "unit": "W/(m·K)",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C",
        "note": "matches Carpenter's 72.85 Btu-in/hr/ft2/°F after conversion to about 10.5 W/(m·K)"
      },
      "method": "Value printed in the producer's physical-properties table",
      "status": "ground",
      "source": "matthey-feni36",
      "where": "Physikalische Eigenschaften, row Wärmeleitfähigkeit bei 20°C",
      "source_detail": {
        "title": "Lamineries Matthey: Invar FeNi36 datasheet",
        "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
        "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
        "kind": "datasheet",
        "license": "Producer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "value": 140,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "form": "cold-rolled strip and foil",
        "unit_in_source": "140 kN/mm2"
      },
      "method": "Value printed in the producer's physical-properties table",
      "status": "ground",
      "source": "matthey-feni36",
      "where": "Physikalische Eigenschaften, row Elastizitätsmodul, E",
      "source_detail": {
        "title": "Lamineries Matthey: Invar FeNi36 datasheet",
        "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
        "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
        "kind": "datasheet",
        "license": "Producer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "value": 141,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "form": "not stated",
        "unit_in_source": "141 kMPa, which is 141 GPa"
      },
      "method": "Value printed in the supplier's physical-properties table",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "PHYSICAL PROPERTIES table, row Modulus of elasticity (Mechanical Properties block)",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "yield_strength",
      "value": 40,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "form": "annealed bar and strip",
        "basis": "typical value, not a guaranteed minimum"
      },
      "method": "Value printed in the manufacturer's typical-mechanical-properties table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Typical mechanical properties, row Annealed bars and strip, YIELD STRENGTH column",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "yield_strength",
      "value": 276,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "form": "not stated",
        "basis": "typical value"
      },
      "method": "Value printed in the supplier's physical-properties table",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "MECHANICAL PROPERTIES block, row Yield strength",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "value": 65,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "form": "annealed bar and strip",
        "basis": "typical value, not a guaranteed minimum"
      },
      "method": "Value printed in the manufacturer's typical-mechanical-properties table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Typical mechanical properties, row Annealed bars and strip, TENSILE STRENGTH column",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "value": 518,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "form": "not stated",
        "basis": "typical value"
      },
      "method": "Value printed in the supplier's physical-properties table",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "MECHANICAL PROPERTIES block, row Tensile strength",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "elongation",
      "value": 35,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "form": "annealed bar and strip",
        "gauge": "2 in (50.8 mm)"
      },
      "method": "Value printed in the manufacturer's typical-mechanical-properties table",
      "status": "ground",
      "source": "carpenter-invar36",
      "where": "Typical mechanical properties, row Annealed bars and strip, ELONGATION column",
      "source_detail": {
        "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
        "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
        "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Manufacturer datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "value": 84,
      "bound": "exact",
      "unit": "µΩ·cm",
      "scope": "material",
      "conditions": {
        "temperature": "not stated"
      },
      "method": "Value printed in the supplier's physical-properties table",
      "status": "ground",
      "source": "nicofe-invar36",
      "where": "PHYSICAL PROPERTIES table, row Electrical resistivity",
      "source_detail": {
        "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
        "id": "Nicofe datasheet IAW3078 v2",
        "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
        "year": 2025,
        "kind": "datasheet",
        "license": "Supplier datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "value": 75,
      "bound": "exact",
      "unit": "µΩ·cm",
      "scope": "material",
      "conditions": {
        "temperature": "not stated",
        "note": "Matthey prints 75; Nicofe prints 84"
      },
      "method": "Value printed in the producer's physical-properties table",
      "status": "ground",
      "source": "matthey-feni36",
      "where": "Physikalische Eigenschaften, row Spezifischer elektrischer Widerstand",
      "source_detail": {
        "title": "Lamineries Matthey: Invar FeNi36 datasheet",
        "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
        "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
        "kind": "datasheet",
        "license": "Producer datasheet, cited not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Dry indoor air; humid air and condensation",
      "headline": "Invar 36 holds up in dry air but its corrosion resistance drops as humidity rises.",
      "effect": "Matthey states that FeNi36 has good corrosion resistance in a dry atmosphere at room temperature, but that the resistance decreases in humid environments. Carpenter rates humidity resistance as \"Good\" on a four-level comparative scale and warns that the rating is for comparison only; Carpenter lists chromium, cadmium and nickel plating and zinc coating among the usual methods for the alloy.\n",
      "rating": "low",
      "conditions": {
        "form": "wrought bar, strip and foil",
        "coating": "none in the datasheets; the alloy is plated for service in humid air"
      },
      "source": "matthey-feni36",
      "where": "Technische Hauptmerkmale, sentence on corrosion resistance (\"in trockener Atmosphäre ... gute Korrosionsbeständigkeit ... nimmt jedoch in feuchten Umgebungen ab\"); see also carpenter-invar36, Corrosion resistance section"
    },
    {
      "environment": "Forging furnace atmosphere containing sulfur",
      "headline": "Long furnace soaks can pit the surface during forging.",
      "effect": "Carpenter warns that soaking Invar 36 in a forging furnace can produce a checked surface through absorption of sulfur from the furnace atmosphere or oxide penetration, and recommends heating quickly at 2000 to 2150 °F (1100 to 1180 °C).\n",
      "rating": "moderate",
      "conditions": {
        "process": "forging",
        "atmosphere": "furnace gases"
      },
      "source": "carpenter-invar36",
      "where": "Workability, Forging paragraph"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "Nickel is the hazard in this alloy. Of 4,778 company reports aggregated by PubChem from the ECHA C&L inventory, 99.9 % classify nickel as a skin sensitiser (H317, may cause an allergic skin reaction) and the signal word is Danger; some notifications also carry carcinogenicity category 2 and respiratory sensitisation category 1. Solid Invar releases little nickel, but grinding and cutting dust does.\n",
        "ghs": [
          "H317"
        ],
        "source": "pubchem-nickel",
        "where": "Safety and Hazards, GHS Classification (CID 935), ECHA C&L notifications summary and hazard statements"
      },
      {
        "text": "Iron is the balance of the alloy. PubChem's aggregation of 6,013 company reports says 74.1 % of them find iron does not meet the GHS hazard criteria, while 15.5 % classify it as a flammable solid (H228). Fine iron powder can ignite and reacts with moisture to give hydrogen, so machining fines are the concern, not solid Invar.\n",
        "ghs": [
          "H228"
        ],
        "source": "pubchem-iron",
        "where": "Safety and Hazards, GHS Classification (CID 23925), ECHA C&L notifications summary and hazard statements"
      }
    ],
    "failure_risks": [
      {
        "mode": "Dimensional drift after machining",
        "trigger": "Cold work left in the part by machining, forming or drawing",
        "consequence": "Carpenter says cold-work stresses cause very slight changes in dimensional stability with time and temperature, detectable only with sensitive instruments; for a telescope spacer that is enough to move focus.",
        "severity": "moderate",
        "source": "carpenter-invar36",
        "where": "Heat treatment, Heat treatment for optimal dimensional stability"
      },
      {
        "mode": "Rust and staining in humid storage",
        "trigger": "Condensation, washing or humid air without plating",
        "consequence": "Matthey says corrosion resistance falls in humid environments; Carpenter rates humidity resistance only as Good on a comparative scale.",
        "severity": "low",
        "source": "matthey-feni36",
        "where": "Technische Hauptmerkmale, corrosion sentence"
      },
      {
        "mode": "Change of length in a magnetic field",
        "trigger": "Exposure to a magnetic field while the part is in service",
        "consequence": "Wikipedia states that Invar's dimensional stability depends on a balance between two magnetic structures, that magnetic fields disturb it, and that the alloy has a propensity to creep.",
        "severity": "moderate",
        "source": "wikipedia-invar",
        "where": "Properties section, paragraph on magnetic structure and dimensional stability"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "For best dimensional stability, heat to 1500 °F (815 °C), hold 30 minutes per inch of thickness, water quench, reheat to 600 °F (315 °C) for one hour, then air cool; Carpenter also ages 24 to 48 hours at 200 °F (93 °C) where temporal stability is needed. Do this before final machining.\n",
        "source": "carpenter-invar36",
        "where": "Heat treatment, Heat treatment for optimal dimensional stability"
      },
      {
        "text": "Forge at 2000 to 2150 °F (1100 to 1180 °C), heat quickly and avoid long soaking, which can check the surface through sulfur pickup.",
        "source": "carpenter-invar36",
        "where": "Workability, Forging"
      },
      {
        "text": "Grinding and cutting dust contains nickel, a skin sensitiser (H317); use dust extraction and gloves, and keep iron fines away from ignition sources.",
        "source": "pubchem-nickel",
        "where": "Safety and Hazards, GHS Classification (CID 935); see also pubchem-iron"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "optics-and-cameras",
      "device": "Metering structures that hold the spacing between optical elements in a space telescope",
      "example": "A 1972 JPL/Itek study for an outer-planets television camera used Invar 36 for all structures that control the spacing between optical elements where athermalisation was required. The report pairs Invar 36 rods with shorter aluminium paths, whose expansions work in opposite directions, and says Super-Invar was rejected because its expansion was less stable over long periods.\n",
      "source": "ntrs-19720025731",
      "where": "Section 3.4.1, paragraphs on structural materials and the athermalisation scheme (pages 3-19 and 3-20)"
    },
    {
      "application": "electronics-and-chips",
      "device": "Semiconductor components, optical and laser benches, precision instruments",
      "example": "Carpenter lists semiconductor components, optical and laser systems, temperature-regulator components and electronic devices as applications; Nicofe lists optoelectronics, optical and laser benches, electronics, scientific instruments and precision tooling.\n",
      "source": "carpenter-invar36",
      "where": "Applications list, first page; see also nicofe-invar36, Applications"
    },
    {
      "application": "cryogenic-fuel",
      "device": "Containers for liquefied natural gas and cryogenic energy storage",
      "example": "Matthey lists containers for LNG tankers and cryogenic energy storage among the applications of FeNi36.",
      "source": "matthey-feni36",
      "where": "Technische Hauptmerkmale, applications sentence"
    }
  ],
  "supply": [
    {
      "subject": "Nickel (the alloying element that sets the expansion)",
      "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": "U.S. critical minerals list (nickel is described as a critical mineral in the USGS Mineral Commodity Summaries 2026 nickel chapter, in the discussion of Executive Order 14285)",
          "listed": true
        }
      ],
      "recycling": "USGS reports that nickel recovered from scrap accounted for approximately 60 % of apparent U.S. consumption in 2025, mostly as nickel in stainless-steel scrap.\n",
      "substitutes": [
        "USGS: low-nickel, duplex or ultrahigh-chromium stainless steels substitute for austenitic grades in construction; nickel-free specialty steels substitute in power generation and petrochemicals; titanium alloys substitute in corrosive environments."
      ],
      "source": "usgs-nickel-2026",
      "where": "World Mine Production and Reserves table, 2025 estimate column (3,900,000 t world total; shares computed from that table by dividing each country's figure by the total); Recycling paragraph\n"
    },
    {
      "subject": "Iron (the 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
        },
        {
          "country": "Russia",
          "share_percent": 3.3,
          "year": 2025
        }
      ],
      "critical_lists": [],
      "recycling": "USGS: none for iron ore; iron and steel scrap is covered in a separate chapter.",
      "substitutes": [],
      "source": "usgs-iron-2026",
      "where": "World Mine Production and Reserves table, 2025 estimate, usable-ore columns (2,600,000 thousand tons world total; shares computed from that table); Recycling line\n"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Carpenter Technology Invar 36 data sheet (v 07-25)",
      "type": "datasheet",
      "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
      "year": 2025
    },
    {
      "title": "Nicofe Invar 36 controlled expansion alloys datasheet v2",
      "type": "datasheet",
      "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
      "year": 2025
    },
    {
      "title": "Lamineries Matthey FeNi36 (Invar) datasheet",
      "type": "datasheet",
      "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf"
    },
    {
      "title": "Itek/JPL, 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: Iron ore",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-ore.pdf",
      "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
    },
    {
      "title": "Wikipedia: Invar (history and magnetic explanation only)",
      "type": "database",
      "url": "https://en.wikipedia.org/wiki/Invar",
      "year": 2026
    }
  ],
  "gaps": [
    "No quantitative corrosion rate, pitting potential or salt-spray result was read; the corrosion section rests on two qualitative datasheet statements. The ScienceDirect paper on cerium in Fe-36Ni corrosion (S2238785424011049) could not be opened from this machine.",
    "The sources disagree on density (8.05 in Nicofe and Carpenter against 8.13 in Matthey), Curie temperature (279 °C in Carpenter and Nicofe against 230 °C in Matthey) and melting point (1427 °C in Carpenter and Nicofe against 1450 °C in Matthey). Both density values are entered; the Curie and melting disagreements are noted here rather than entered twice.",
    "The UNS number is printed three ways: K93600 (Matthey, approximately), K93601 and K93603 (Carpenter) and K93603 (Nicofe). All three are recorded in the identity formula.",
    "No vacuum outgassing, radiation, atomic-oxygen or thermal-vacuum data for Invar 36 were read. The only space source is the 1972 JPL optics study, which is a design report, not a test.",
    "NIST publishes cryogenic curve fits for Invar (4 to 300 K) but they are coefficients, not printed values; they were not reduced to numbers here, so the only cryogenic CTE entered is Matthey's -240 to -18 °C entry.",
    "The taxonomy has no controlled-expansion-alloy type, so this profile is filed under nickel-superalloys, the nearest bucket; Invar is not a superalloy.",
    "Hardness (70 HRB annealed, Carpenter) is not in property-canon.yaml and was left out rather than inventing a benchmark name.",
    "No cost or lead-time data were read."
  ],
  "story": {
    "why": "Invar 36 works because its thermal expansion nearly vanishes near room temperature: 1.3 ppm/K up to 93 °C, where ordinary steel would be about ten times higher. A structure made of it barely changes length when the temperature moves, which is what a telescope needs to keep its mirrors and detectors at a fixed spacing. The cost is a soft metal (276 MPa yield annealed), a sensitivity to humidity, and a length that drifts unless the part is stress-relieved before final machining.\n",
    "uses": [
      {
        "where": "Space telescope optics",
        "line": "A 1972 JPL/Itek study used Invar 36 for every structure that set the spacing between optical elements, pairing Invar rods with shorter aluminium paths whose expansions oppose each other."
      },
      {
        "where": "Precision instruments and laser benches",
        "line": "Carpenter lists semiconductor components, optical and laser systems and temperature-regulator parts; Nicofe lists optoelectronics, optical benches and precision tooling."
      },
      {
        "where": "Cryogenic vessels",
        "line": "Matthey lists LNG tanker containers and cryogenic energy storage."
      }
    ],
    "can_do": [
      {
        "label": "Expansion",
        "line": "1.3 ppm/K to 93 °C, 2.11 to 149 °C and 4.18 to 260 °C (Carpenter); 1.18 over 30-100 °C (Nicofe); 1.8 between -240 and -18 °C (Matthey).",
        "benchmark": "cte",
        "scope": "material"
      },
      {
        "label": "Stiffness",
        "line": "140 GPa (Matthey) and 141 GPa (Nicofe).",
        "benchmark": "elastic_modulus",
        "scope": "material"
      },
      {
        "label": "Strength",
        "line": "276 MPa yield and 518 MPa tensile (Nicofe); 40 ksi yield and 65 ksi tensile in the annealed condition (Carpenter).",
        "benchmark": "yield_strength",
        "scope": "material"
      },
      {
        "label": "Melting",
        "line": "1427 °C melting range (Carpenter).",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Conductivity",
        "line": "10.5 W/(m·K) at 20 °C (Matthey), the same as Carpenter's 72.85 Btu-in/hr/ft2/°F.",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      }
    ],
    "compare": "Invar 36 is the reference low-expansion metal, and everything else in this comparison is judged against it. Its expansion of 1.3 ppm/K near room temperature is roughly a tenth that of carbon steel and far below aluminium, which is why optical structures mix the two: the aluminium moves, the Invar barely does, and the difference can be arranged to cancel. It pays for that with low strength (276 MPa yield), a density of 8.05 g/cm3, and a corrosion resistance that Matthey says falls in humid air.\n",
    "compare_rows": [
      {
        "label": "Thermal expansion",
        "benchmark": "cte",
        "scope": "material"
      },
      {
        "label": "Stiffness",
        "benchmark": "elastic_modulus",
        "scope": "material"
      },
      {
        "label": "Strength",
        "benchmark": "yield_strength",
        "scope": "material"
      }
    ],
    "handling": [
      "Stress-relieve before final machining: heat, water-quench, reheat and age, following the schedule in the handling notes.",
      "Forge quickly at temperature and do not soak, or the surface can check.",
      "Keep grinding dust and iron fines away from ignition sources, and protect skin from nickel-bearing dust."
    ],
    "good_for": [
      "Holding optical spacing across temperature swings: 1.3 ppm/K near room temperature.",
      "Cryogenic instruments: 1.8 ppm/K between -240 and -18 °C.",
      "Precision instruments, laser benches and semiconductor components."
    ],
    "watch_out": [
      "Humid air: corrosion resistance falls, and the datasheets offer no quantitative rate.",
      "Dimensional drift from cold work unless the part is stress-relieved before final machining.",
      "Magnetic fields disturb the dimensional stability, and the alloy can creep."
    ],
    "verdict": "Invar 36 is the reference low-expansion metal: unmatched for holding a dimension near room temperature, but soft, rust-prone in humid air and only as stable as its heat treatment. Use it where the dimension matters more than the strength.\n",
    "recipe": {
      "line": "Invar 36 is a single-phase face-centred-cubic iron-nickel alloy of about 36 wt% nickel and 64 wt% iron, with manganese at 0.35 wt% nominal (maximum 0.60), silicon at 0.20 (maximum 0.40) and carbon at 0.02 (maximum 0.15), as Carpenter prints it; Matthey widens the nickel range to 35.0-37.0 wt%. It is supplied as wrought bar, strip, plate and wire.\n",
      "parts": [
        {
          "name": "Iron",
          "symbol": "Fe",
          "role": "The magnetic host that makes the Invar effect possible: the alloy's expansion cancels because of the way its two magnetic states respond to heat.",
          "atomic_weight": 55.84,
          "share_note": "balance (about 64 wt%)",
          "source": "pubchem-iron",
          "where": "Molecular weight 55.84, PubChem CID 23925"
        },
        {
          "name": "Nickel",
          "symbol": "Ni",
          "role": "Sets the expansion minimum at about 36 wt%; away from that composition the alloy expands like ordinary steel.",
          "atomic_weight": 58.693,
          "share_percent": 36,
          "share_high": 37,
          "share_note": "wt%, nominal 36.00",
          "source": "matthey-feni36",
          "where": "Chemical composition table, Ni 35.0-37.0; atomic weight 58.693, PubChem CID 935"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The alloy is mostly iron, but the nickel in it is the health hazard, and machining produces both nickel-bearing dust and fine iron.",
        "points": [
          {
            "label": "Skin",
            "line": "Nickel is classified H317 (may cause an allergic skin reaction) by 99.9 % of the company reports aggregated by PubChem, and some reports add carcinogenicity category 2 and respiratory sensitisation."
          },
          {
            "label": "Dust and fines",
            "line": "Iron powder is a flammable solid (H228) in 15.5 % of reports; fine iron reacts with moisture to release hydrogen."
          }
        ],
        "level": 1,
        "verdict": "Nickel sensitiser, iron fines flammable"
      },
      {
        "title": "In service",
        "lead": "The low expansion is the point of the alloy, but cold work and humidity both work against it.",
        "points": [
          {
            "label": "Dimensional drift",
            "line": "Cold-work stresses change the length very slightly with time and temperature; Carpenter's stabilising heat treatment is the fix."
          },
          {
            "label": "Corrosion",
            "line": "Corrosion resistance is good in dry air but falls in humid environments, so unprotected parts stain."
          }
        ],
        "level": 2,
        "verdict": "Stable only if stress-relieved"
      },
      {
        "title": "In space",
        "lead": "The space record found here is a design study, not a flight qualification.",
        "points": [
          {
            "label": "What the report says",
            "line": "The 1972 JPL study chose Invar 36 for metering structures and rejected Super-Invar for long-term instability of its expansion."
          },
          {
            "label": "What is missing",
            "line": "No thermal-vacuum, outgassing or radiation test of Invar 36 was read."
          }
        ],
        "level": 1,
        "verdict": "Design data only"
      }
    ]
  },
  "updated": "2026-10-19",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 22,
    "unreachable": 1,
    "caveats": 4,
    "note": "Values were read by an AI assistant on 2026-10-19 from the pages and PDFs named in each entry: the Carpenter, Nicofe and Matthey PDFs were downloaded and converted with pdftotext, the JPL report text was extracted from the NTRS PDF, and the two USGS chapters and the PubChem records came from their PDFs and REST API. Unreachable: the ScienceDirect paper on cerium in Fe-36Ni corrosion. Caveats: strengths are typical values of one manufacturer, density and Curie temperature differ between sources, the cryogenic CTE covers only -240 to -18 °C, and the space use comes from a 1972 design report rather than a test.\n"
  },
  "sources": {
    "carpenter-invar36": {
      "title": "Carpenter Technology: Invar 36 data sheet (v 07-25)",
      "id": "Carpenter Technology data sheet, Invar 36, v 07-25",
      "url": "https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/Invar%2036.pdf",
      "year": 2025,
      "kind": "datasheet",
      "license": "Manufacturer datasheet, cited not reproduced"
    },
    "nicofe-invar36": {
      "title": "Nicofe: Invar 36 controlled expansion alloys datasheet v2",
      "id": "Nicofe datasheet IAW3078 v2",
      "url": "https://www.nicofe.com/wp-content/uploads/2025/12/IAW3078-Nicofe-INVAR-36-A4-datasheet-v2.pdf",
      "year": 2025,
      "kind": "datasheet",
      "license": "Supplier datasheet, cited not reproduced"
    },
    "matthey-feni36": {
      "title": "Lamineries Matthey: Invar FeNi36 datasheet",
      "id": "Lamineries MATTHEY, FeNi36-Invar, v22D",
      "url": "https://www.matthey.ch/fileadmin/user_upload/downloads/fichetechnique/DE/FeNi36-Invar_v22D.pdf",
      "kind": "datasheet",
      "license": "Producer datasheet, cited not reproduced"
    },
    "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"
    },
    "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-iron-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"
    },
    "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), Safety and Hazards",
      "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"
    },
    "wikipedia-invar": {
      "title": "Wikipedia: Invar",
      "id": "Wikipedia, Invar (revision read 2026-10-19)",
      "url": "https://en.wikipedia.org/wiki/Invar",
      "year": 2026,
      "kind": "web",
      "license": "CC BY-SA 4.0 (cited, not reproduced)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/invar-36/"
}