{ "spore": "profile", "id": "molybdenum", "spore_version": "0.2", "family": "refractory-metals", "name": "Molybdenum", "abbreviation": "Mo", "role": "refractory structural and alloying metal", "category": "metals", "type": "refractory-metals", "summary": "Molybdenum is the element Mo, a refractory metal with a melting point of 2623 °C (PubChem record) and a density of 10.22 g/cm3 at 20 °C (Plansee). Most of it goes into steel, cast iron and superalloys. In air it is not easily oxidised at ordinary temperature, but above 400 °C it forms the volatile trioxide MoO3 (PubChem). A laboratory rod made from electron-beam-melted 99.97 % molybdenum and annealed 1 h at 1315 °C had a yield strength of 265 MPa and a tensile strength of 411 MPa at 25 °C (NASA TM X-2576).\n", "best_for": "High-temperature strength and heat conduction: 2623 °C melting point and 142 W/(m·K) thermal conductivity at 20 °C, in vacuum or inert service", "weakest_at": "Oxidation in air above about 400 °C, where it forms volatile MoO3, and toughness at room temperature in as-rolled sheet (ductile-brittle transition above 25 °C in the NASA study)", "identity": { "formula": "Mo (element, atomic number 42), unalloyed body-centred cubic metal", "cas": "7439-98-7", "designations": [ { "system": "UNS", "code": "R03610", "note": "isotropic pure molybdenum, ASTM B1024 grades 1 and 2 (unalloyed monolithic forms)", "source": "astm-b1024", "where": "Scope sections 1.2 and 1.3, Grade 1 (UNS R03610) and Grade 2 (UNS R03610)" }, { "system": "ASTM", "code": "B1024", "note": "isotropic pure molybdenum, monolithic forms", "source": "astm-b1024", "where": "Title: Standard Specification for Isotropic Pure Molybdenum" }, { "system": "ASTM", "code": "B387", "note": "bar, rod and wire; unalloyed Molybdenum 360, 361 and 365 are listed in the scope", "source": "astm-b387", "where": "Title and scope section 1.1, unalloyed grades 360, 361 and 365" }, { "system": "ASTM", "code": "B386", "note": "plate, sheet, strip, foil and ribbon; unalloyed Molybdenum 360, 361 and 365 are listed in the scope", "source": "astm-b386", "where": "Title and scope section 1.1, unalloyed grades 360, 361 and 365" } ], "source": "pubchem-mo", "where": "Other Identifiers, CAS entry 7439-98-7 in the PubChem record for molybdenum (CID 23932)" }, "tags": { "environments": [], "stresses": [], "applications": [ "structures", "electronics-and-chips", "thermal-control" ] }, "properties": [ { "benchmark": "density", "label": "Density of pure molybdenum at 20 °C", "value": 10.22, "bound": "exact", "unit": "g/cm3", "scope": "material", "conditions": { "temperature": "20 °C", "form": "pure molybdenum metal, no grade stated" }, "method": "Value printed on the manufacturer material page", "status": "ground", "source": "plansee-mo", "where": "Facts table, row Density, condition 20 °C", "source_detail": { "title": "Plansee, Molybdenum material page (facts table: physical properties at 20 °C)", "url": "https://www.plansee.com/en/materials/molybdenum.html", "kind": "datasheet", "license": "Manufacturer web page (cited, not reproduced)" } }, { "benchmark": "melting_point", "label": "Melting point of molybdenum", "value": 2623, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "unit_in_source": "4752 °F (NIOSH, 2024) and 2622 °C, 2617 °C from other entries", "pressure": "not stated" }, "method": "Value printed in the Experimental Properties section of the PubChem record", "status": "ground", "source": "pubchem-mo", "where": "Chemical and Physical Properties, Experimental Properties, Melting Point, entry 2623 °C", "source_detail": { "title": "PubChem compound record: Molybdenum (CID 23932), including ECHA C&L notifications, NIOSH and vapour pressure entries", "id": "CAS 7439-98-7, UNII 81AH48963U", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML", "kind": "database", "license": "PubChem (NCBI), public domain; sections attributed to ECHA, NIOSH and others" } }, { "benchmark": "boiling_point", "label": "Boiling point of molybdenum", "value": 4639, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "pressure": "760 mmHg", "unit_in_source": "8717 °F at 760 mmHg (NIOSH, 2024)" }, "method": "Value printed in the Experimental Properties section of the PubChem record", "status": "ground", "source": "pubchem-mo", "where": "Chemical and Physical Properties, Experimental Properties, Boiling Point, entry 4639 °C @760 [mm Hg]", "source_detail": { "title": "PubChem compound record: Molybdenum (CID 23932), including ECHA C&L notifications, NIOSH and vapour pressure entries", "id": "CAS 7439-98-7, UNII 81AH48963U", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML", "kind": "database", "license": "PubChem (NCBI), public domain; sections attributed to ECHA, NIOSH and others" } }, { "benchmark": "thermal_conductivity", "label": "Thermal conductivity of pure molybdenum at 20 °C", "value": 142, "bound": "exact", "unit": "W/(m·K)", "scope": "material", "conditions": { "temperature": "20 °C", "form": "pure molybdenum metal, no grade stated" }, "method": "Value printed on the manufacturer material page", "status": "ground", "source": "plansee-mo", "where": "Facts table, row Thermal conductivity, condition 20 °C", "source_detail": { "title": "Plansee, Molybdenum material page (facts table: physical properties at 20 °C)", "url": "https://www.plansee.com/en/materials/molybdenum.html", "kind": "datasheet", "license": "Manufacturer web page (cited, not reproduced)" } }, { "benchmark": "cte", "label": "Coefficient of thermal expansion of pure molybdenum at 20 °C", "value": 5.2, "bound": "exact", "unit": "ppm/K", "scope": "material", "conditions": { "temperature": "20 °C", "unit_in_source": "5.2 × 10-6 m/(m·K), equal to ppm/K" }, "method": "Value printed on the manufacturer material page", "status": "ground", "source": "plansee-mo", "where": "Facts table, row Coefficient of linear thermal expansion, condition 20 °C", "source_detail": { "title": "Plansee, Molybdenum material page (facts table: physical properties at 20 °C)", "url": "https://www.plansee.com/en/materials/molybdenum.html", "kind": "datasheet", "license": "Manufacturer web page (cited, not reproduced)" } }, { "benchmark": "specific_heat", "label": "Specific heat of pure molybdenum at 20 °C", "value": 0.25, "bound": "exact", "unit": "J/(g·K)", "scope": "material", "conditions": { "temperature": "20 °C", "form": "pure molybdenum metal, no grade stated" }, "method": "Value printed on the manufacturer material page", "status": "ground", "source": "plansee-mo", "where": "Facts table, row Specific heat, condition 20 °C", "source_detail": { "title": "Plansee, Molybdenum material page (facts table: physical properties at 20 °C)", "url": "https://www.plansee.com/en/materials/molybdenum.html", "kind": "datasheet", "license": "Manufacturer web page (cited, not reproduced)" } }, { "benchmark": "electrical_resistivity", "label": "Specific electrical resistance of pure molybdenum at 20 °C", "value": 0.056, "bound": "exact", "unit": "Ω·mm²/m", "scope": "material", "conditions": { "temperature": "20 °C", "form": "pure molybdenum metal, no grade stated" }, "method": "Value printed on the manufacturer material page", "status": "ground", "source": "plansee-mo", "where": "Facts table, row Specific electrical resistance, condition 20 °C", "source_detail": { "title": "Plansee, Molybdenum material page (facts table: physical properties at 20 °C)", "url": "https://www.plansee.com/en/materials/molybdenum.html", "kind": "datasheet", "license": "Manufacturer web page (cited, not reproduced)" } }, { "benchmark": "yield_strength", "label": "Yield strength, 0.2 percent offset, annealed rod at 25 °C", "value": 265, "bound": "exact", "unit": "MPa", "scope": "material", "conditions": { "material": "electron-beam-melted molybdenum, 99.97 % Mo, laboratory ingot (not a standard product)", "form": "rod, swaged", "temper": "annealed 1 h at 1315 °C (2400 °F)", "temperature": "25 °C (75 °F)", "unit_in_source": "MN/m2 (38.4 ksi)" }, "method": "Value printed in a NASA table of tensile results for electron-beam-melted molybdenum", "status": "ground", "source": "nasa-tm-x2576", "where": "Table IV, rod group, 1315 °C anneal row, test temperature 25 °C, column 0.2-percent offset yield strength", "source_detail": { "title": "NASA TM X-2576: Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys (Klopp and Witzke, Lewis Research Center, 1972)", "id": "NTRS 19720017873", "url": "https://ntrs.nasa.gov/api/citations/19720017873/downloads/19720017873.pdf", "year": 1972, "kind": "report", "license": "public domain (NASA)" } }, { "benchmark": "ultimate_tensile_strength", "label": "Ultimate tensile strength, annealed rod at 25 °C", "value": 411, "bound": "exact", "unit": "MPa", "scope": "material", "conditions": { "material": "electron-beam-melted molybdenum, 99.97 % Mo, laboratory ingot (not a standard product)", "form": "rod, swaged", "temper": "annealed 1 h at 1315 °C (2400 °F)", "temperature": "25 °C (75 °F)", "unit_in_source": "MN/m2 (59.6 ksi)" }, "method": "Value printed in a NASA table of tensile results for electron-beam-melted molybdenum", "status": "ground", "source": "nasa-tm-x2576", "where": "Table IV, rod group, 1315 °C anneal row, test temperature 25 °C, column ultimate tensile strength", "source_detail": { "title": "NASA TM X-2576: Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys (Klopp and Witzke, Lewis Research Center, 1972)", "id": "NTRS 19720017873", "url": "https://ntrs.nasa.gov/api/citations/19720017873/downloads/19720017873.pdf", "year": 1972, "kind": "report", "license": "public domain (NASA)" } }, { "benchmark": "recrystallization_temperature", "label": "Recrystallization temperature of unalloyed molybdenum sheet, 100 percent in 1 hour", "value": 925, "bound": "exact", "unit": "°C", "scope": "material", "conditions": { "material": "electron-beam-melted unalloyed molybdenum sheet", "cold_work": "81 to 92 percent", "time": "1 hour", "unit_in_source": "1700 °F" }, "method": "Value stated in the recrystallization section of a NASA technical memorandum", "status": "ground", "source": "nasa-tm-x2576", "where": "Recrystallization and Grain Growth section, text on unalloyed molybdenum sheet, and Table VII", "source_detail": { "title": "NASA TM X-2576: Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys (Klopp and Witzke, Lewis Research Center, 1972)", "id": "NTRS 19720017873", "url": "https://ntrs.nasa.gov/api/citations/19720017873/downloads/19720017873.pdf", "year": 1972, "kind": "report", "license": "public domain (NASA)" } }, { "benchmark": "vapor_pressure", "label": "Vapour pressure of molybdenum (solid)", "value": 1, "bound": "exact", "unit": "Pa", "scope": "material", "conditions": { "temperature": "2469 °C (solid)", "unit_in_source": "1 Pa at 2469 °C (solid)" }, "method": "Value listed in the Vapor Pressure section of the PubChem record", "status": "ground", "source": "pubchem-mo", "where": "Chemical and Physical Properties, Experimental Properties, Vapor Pressure, entry 1 Pa at 2469 °C (solid)", "source_detail": { "title": "PubChem compound record: Molybdenum (CID 23932), including ECHA C&L notifications, NIOSH and vapour pressure entries", "id": "CAS 7439-98-7, UNII 81AH48963U", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML", "kind": "database", "license": "PubChem (NCBI), public domain; sections attributed to ECHA, NIOSH and others" } }, { "benchmark": "heat_of_vaporization", "label": "Heat of vaporization of molybdenum", "value": 491, "bound": "exact", "unit": "kJ/mol", "scope": "material", "conditions": { "basis": "not stated in the record" }, "method": "Value listed in the Experimental Properties section of the PubChem record", "status": "ground", "source": "pubchem-mo", "where": "Chemical and Physical Properties, Experimental Properties, Heat of Vaporization, entry 491 kJ/mol", "source_detail": { "title": "PubChem compound record: Molybdenum (CID 23932), including ECHA C&L notifications, NIOSH and vapour pressure entries", "id": "CAS 7439-98-7, UNII 81AH48963U", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML", "kind": "database", "license": "PubChem (NCBI), public domain; sections attributed to ECHA, NIOSH and others" } }, { "benchmark": "molar_heat_capacity", "label": "Molar heat capacity of molybdenum at 25 °C", "value": 24.06, "bound": "exact", "unit": "J/(mol·K)", "scope": "material", "conditions": { "temperature": "25 °C", "pressure": "100 kPa (760 mm Hg)" }, "method": "Value listed in the Other Experimental Properties section of the PubChem record", "status": "ground", "source": "pubchem-mo", "where": "Chemical and Physical Properties, Experimental Properties, Other Experimental Properties, molar heat capacity entry", "source_detail": { "title": "PubChem compound record: Molybdenum (CID 23932), including ECHA C&L notifications, NIOSH and vapour pressure entries", "id": "CAS 7439-98-7, UNII 81AH48963U", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML", "kind": "database", "license": "PubChem (NCBI), public domain; sections attributed to ECHA, NIOSH and others" } } ], "corrosion": [ { "environment": "Air at ordinary temperature", "headline": "Molybdenum is not easily oxidised by air or water at ordinary temperature.", "effect": "The PubChem record quotes a source: the metal is not easily oxidised by air or water at ordinary temperature, and it has poor oxidation resistance at higher temperature.", "rating": "low", "conditions": { "temperature": "ordinary temperature (not stated numerically)" }, "source": "pubchem-mo", "where": "Spectral Information, Other Spectra entry" }, { "environment": "Air above 400 °C", "headline": "Above 400 °C molybdenum forms a highly volatile trioxide, MoO3, and above 700 °C the oxidation becomes so severe that it needs a protective coating.", "effect": "The PubChem record says that when heated above 400 °C molybdenum yields a highly volatile trioxide (MoO3), and above 700 °C oxidation is so severe that use is possible only if the metal is protected by a covering layer of an oxidation-resistant metal, an alloy, or a silicon deposit.", "rating": "severe", "conditions": { "temperature": "above 400 °C in air", "unit_in_source": "400 °C and 700 °C as printed" }, "source": "pubchem-mo", "where": "Spectral Information, Other Spectra entry" }, { "environment": "Acids and water", "headline": "Molybdenum is insoluble in water and is attacked by hot concentrated sulphuric or nitric acid.", "effect": "The PubChem record gives insoluble in water, soluble in nitric acid and sulphuric acid, slightly soluble in hydrochloric acid, and insoluble in hydrofluoric acid and dilute sulphuric acid. The record also says it reacts with nitric acid, hot concentrated sulphuric acid, and fused potassium chlorate or nitrate.", "rating": "moderate", "conditions": { "basis": "solubility statements as printed, no rate given" }, "source": "pubchem-mo", "where": "Experimental Properties, Solubility entries" } ], "risks": { "hazards": [ { "text": "PubChem aggregates ECHA C&L notifications for molybdenum (1523 company reports). Among the notifications, H228 flammable solid is given for 30 % of reports that gave codes, H361 suspected of damaging fertility or the unborn child for 29.5 %, and H225 for 11.6 %. The record says 874 of 1523 reports (57.4 %) do not meet GHS criteria. The notified classification is not specific to form, so it is not a rating for solid metal.", "ghs": [ "H228", "H361", "H225" ], "source": "pubchem-mo", "where": "Safety and Hazards, GHS Classification, GHS Hazard Statements and ECHA C&L Notifications Summary" }, { "text": "Other PubChem notifications give H315 (causes skin irritation), H319 (causes serious eye irritation) and H335 (may cause respiratory irritation), signal word Warning.", "ghs": [ "H315", "H319", "H335" ], "source": "pubchem-mo", "where": "Safety and Hazards, GHS Classification, second notification block" }, { "text": "The PubChem record gives the NIOSH Pocket Guide excerpt: dust and fumes irritate the eyes and respiratory tract. Exposure routes are inhalation, ingestion and skin or eye contact. Target organs are the eyes, respiratory system, liver and kidneys.", "ghs": [], "source": "pubchem-mo", "where": "Safety and Hazards, Health Hazards, NIOSH excerpt" } ], "failure_risks": [ { "mode": "Oxide loss in hot air", "trigger": "Metal heated above 400 °C in air", "consequence": "Molybdenum forms the volatile trioxide MoO3, so the metal is lost from the part. Above 700 °C a protective coating is needed.", "severity": "critical", "source": "pubchem-mo", "where": "Spectral Information, Other Spectra entry" }, { "mode": "Softening of cold-worked sheet", "trigger": "Cold-worked unalloyed sheet (81 to 92 percent cold work) held 1 hour at 925 °C", "consequence": "The sheet recrystallises fully, so it loses the strength it gained from cold work. The source gives the temperature only and does not measure the strength after annealing.", "severity": "moderate", "source": "nasa-tm-x2576", "where": "Recrystallization and Grain Growth section and Table VII" }, { "mode": "Brittleness at room temperature in as-rolled sheet", "trigger": "Sheet used as rolled, not annealed", "consequence": "The NASA table gives an approximate ductile-brittle transition above 25 °C (more than 75 °F) for as-rolled sheet, so the sheet can break in a brittle way near room temperature. The table is an OCR scan, so this value should be checked against the page image.", "severity": "moderate", "source": "nasa-tm-x2576", "where": "Table IV, row 100 Mo sheet (a) as rolled, not annealed, last column" } ], "side_effects": [], "handling": [ { "text": "Keep dust and fumes out of breathing zones and off the eyes. The PubChem record cites the NIOSH Pocket Guide for irritation of the eyes, nose and throat in animals and for liver and kidney effects at high exposure.", "source": "pubchem-mo", "where": "Health Hazards, NIOSH excerpt" }, { "text": "Use an oxidation-resistant coating or a vacuum or inert atmosphere for hot service, because the metal oxidises to a volatile oxide above 400 °C in air.", "source": "pubchem-mo", "where": "Spectral Information, Other Spectra entry" } ], "mitigations": [] }, "uses": [ { "application": "structures", "device": "Alloying agent in steel, cast iron and superalloys", "example": "The USGS says molybdenum is used principally as an alloying agent in cast iron, steel and superalloys, and that in 2025 U.S. apparent consumption was estimated at 34,000 tons of molybdenum content.", "source": "usgs-mcs2026-molybdenum", "where": "Domestic Production and Use paragraph and Salient Statistics table, row Apparent consumption" }, { "application": "electronics-and-chips", "device": "Conductive metal layers in thin-film transistors", "example": "The PubChem record says molybdenum is found in some electronic applications as the conductive metal layers in thin-film transistors (TFTs).", "source": "pubchem-mo", "where": "Use and Manufacturing, Uses section" }, { "application": "thermal-control", "device": "Resistance elements in electric furnaces", "example": "The PubChem record lists resistance elements for electric furnaces among molybdenum uses. The USGS lists graphite, tantalum and tungsten as potential substitutes for molybdenum in refractory materials for high-temperature electric furnaces.", "source": "pubchem-mo", "where": "Use and Manufacturing, Uses section; USGS Substitutes paragraph" } ], "supply": [ { "subject": "Molybdenum (mine production, molybdenum content)", "producers": [ { "country": "China", "share_percent": 37.3, "year": 2025 }, { "country": "Chile", "share_percent": 16.2, "year": 2025 }, { "country": "United States", "share_percent": 15.4, "year": 2025 }, { "country": "Peru", "share_percent": 15, "year": 2025 }, { "country": "Mexico", "share_percent": 6.5, "year": 2025 } ], "critical_lists": [], "recycling": "The USGS says molybdenum is recycled as a component of catalysts, ferrous scrap and superalloy scrap, and that recycled molybdenum may be as much as 30 % of apparent supply. There is no separate recovery process for secondary molybdenum from its alloys.", "substitutes": [ "USGS: little substitution in steels and cast irons; boron, chromium, niobium and vanadium in alloy steels; tungsten in tool steels; graphite, tantalum and tungsten for refractory materials in high-temperature electric furnaces." ], "source": "usgs-mcs2026-molybdenum", "where": "World Mine Production and Reserves table, mine production 2025e (world total 260,000 tons; shares calculated by Space Mushroom from the country values 97,000; 42,000; 40,000; 39,000; 17,000). Substitutes and Events, Trends and Issues paragraphs. The top five producers sum to 90 % of world production, as the USGS also states." } ], "media": [], "documents": [ { "title": "USGS Mineral Commodity Summaries 2026: Molybdenum", "type": "report", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf", "year": 2026 }, { "title": "PubChem compound record for molybdenum (CID 23932), XML view", "type": "database", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML" }, { "title": "Plansee material page: molybdenum (physical properties, 20 °C)", "type": "datasheet", "url": "https://www.plansee.com/en/materials/molybdenum.html" }, { "title": "Klopp and Witzke, Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys, NASA TM X-2576 (1972)", "type": "report", "url": "https://ntrs.nasa.gov/api/citations/19720017873/downloads/19720017873.pdf", "year": 1972 }, { "title": "ASTM B1024/B1024M-23: Standard Specification for Isotropic Pure Molybdenum", "type": "standard", "url": "https://standards.nimonik.com/products/astm/b1024-b1024m/", "year": 2023 }, { "title": "ASTM B387/B387M-23: Standard Specification for Molybdenum and Molybdenum Alloy Bar, Rod, and Wire", "type": "standard", "url": "https://store.astm.org/b0387_b0387m-23.html", "year": 2023 }, { "title": "Wikipedia: Molybdenum (crystal structure, molybdenite ore, history)", "type": "database", "url": "https://en.wikipedia.org/wiki/Molybdenum", "year": 2026 }, { "title": "ASTM B386/B386M-25: Standard Specification for Molybdenum and Molybdenum Alloy Plate, Sheet, Strip, Foil, and Ribbon", "type": "standard", "url": "https://store.astm.org/b0386_b0386m-25.html", "year": 2025 } ], "gaps": [ "No EN, W.Nr., DIN or JIS designation for pure molybdenum was printed in any source opened in this run. UNS R03630 was searched for and not confirmed; the only UNS code found for unalloyed molybdenum is R03610 (ASTM B1024).", "Young's modulus and Poisson's ratio for pure molybdenum are not recorded. The Wikipedia elastic-properties data page gives 329 GPa and 0.31 at room temperature (CRC), but the brief limits Wikipedia to composition and history, so the value was not used. The Princeton glossary (320 GPa) and matmatch pages were not readable in this run.", "The Plansee page returned Access Denied to the automated curl check, so the values from it (density, thermal conductivity, CTE, specific heat, electrical resistance) were read with the web-fetch tool in this run but cannot be checked by verify-values. The page prints no modulus, tensile, yield, hardness or recrystallization values.", "Mechanical data rest on one laboratory rod condition (electron-beam-melted 99.97 % molybdenum, annealed 1315 °C, tested at 25 °C) and one sheet recrystallization figure. No standard-product minimum tensile or yield value from ASTM B386 or B387 was found in the scope pages opened; those pages print scope and grade names only.", "Hardness of pure molybdenum was not found in a readable source. The Advent RM and aircraftmaterials pages were garbled, and the Elmet page could not be reached.", "The as-rolled sheet transition temperature (above 25 °C) is read from an OCR table in a NASA scan and should be checked against the page image.", "Boiling point, heat of vaporization and molar heat capacity come from the PubChem record, whose original sources are not named in the fetched text.", "Recrystallization temperature is stored under a non-canonical benchmark name (recrystallization_temperature) because no canonical name in property-canon.yaml fits. Boiling point and heat of vaporization are also non-canonical names.", "The PubChem GHS notifications are not specific to the metal form; the H228 and H361 shares may come from powder or compound notifications, so they are shown as aggregated ECHA data only.", "The USGS molybdenum summary does not state a critical-minerals list membership, and the 2025 U.S. critical-minerals list was not opened. The critical_lists field is therefore empty.", "No exposure limits (OSHA PEL, ACGIH TLV) were read; PubChem gives only the OSHA sampling method numbers.", "Radiation effects, outgassing (NASA total mass loss) and atomic-oxygen erosion of molybdenum were not searched or not found in an accepted source.", "Process steps: the USGS says roasting plants convert molybdenum concentrate to molybdic oxide, from which metal powder is made. The powder-to-ingot route is taken from the NASA laboratory melt, not from a primary production reference.", "Electrical conductivity is not recorded; the Plansee page gives 17.9 × 10^6 S/m at 20 °C, which was not converted and is represented by the resistivity line instead.", "Mo-99 and biological roles of molybdenum are outside the scope of this profile." ], "story": { "why": "Molybdenum is a refractory metal, with a melting point of 2623 °C (PubChem) and a density of 10.22 g/cm3 at 20 °C (Plansee). It is used mostly as an alloying agent in steel, cast iron and superalloys, according to the USGS. The pure metal also appears in thin-film transistor layers and in electric-furnace resistance elements, according to the PubChem record.", "uses": [ { "where": "Steel and superalloys", "line": "The USGS says molybdenum is used principally as an alloying agent in cast iron, steel and superalloys, and it estimates U.S. apparent consumption in 2025 at 34,000 tons of molybdenum content." }, { "where": "Thin-film electronics", "line": "The PubChem record says molybdenum is found in some electronic applications as the conductive metal layers in thin-film transistors." }, { "where": "Furnaces", "line": "The PubChem record lists resistance elements for electric furnaces among its uses." } ], "can_do": [ { "label": "Stay solid when hot", "line": "Molybdenum melts at 2623 °C according to the PubChem record, and boils at 4639 °C at 760 mmHg.", "benchmark": "melting_point", "scope": "material", "value": "2623 °C" }, { "label": "Carry heat", "line": "Thermal conductivity at 20 °C is 142 W/(m·K), as printed by Plansee for pure molybdenum.", "benchmark": "thermal_conductivity", "scope": "material", "value": "142 W/(m·K)" }, { "label": "Hold strength when annealed", "line": "A laboratory rod of electron-beam-melted 99.97 % molybdenum, annealed 1 h at 1315 °C, had a yield strength of 265 MPa and a tensile strength of 411 MPa at 25 °C.", "scope": "material", "value": "265 MPa yield" }, { "label": "Weight", "line": "Density is 10.22 g/cm3 at 20 °C, according to the Plansee page for pure molybdenum.", "benchmark": "density", "scope": "material", "value": "10.22 g/cm3" }, { "label": "Expansion", "line": "The coefficient of linear thermal expansion is 5.2 ppm/K at 20 °C, as printed by Plansee.", "benchmark": "cte", "scope": "material", "value": "5.2 ppm/K" } ], "compare": "The USGS names graphite, tantalum and tungsten as potential substitutes for molybdenum in refractory materials for high-temperature electric furnaces, and boron, chromium, niobium and vanadium as alternatives in alloy steels. Molybdenum is hard to replace in steels and cast irons, where the USGS says there is little substitution.", "compare_rows": [ { "label": "Density", "benchmark": "density", "scope": "material" }, { "label": "Thermal conductivity", "benchmark": "thermal_conductivity", "scope": "material" }, { "label": "Thermal expansion", "benchmark": "cte", "scope": "material" } ], "handling": [ "Keep dust and fumes out of the breathing zone and away from the eyes.", "Protect the metal from air above 400 °C with a coating, a vacuum or an inert gas.", "If cold work must be kept, hold cold-worked sheet below the 925 °C recrystallisation temperature (100 % recrystallised in 1 hour, NASA TM X-2576)." ], "good_for": [ "High-temperature service in vacuum or inert gas: melting point 2623 °C (PubChem).", "Steel and superalloy additions: the main end use, according to the USGS.", "Conducting heat: 142 W/(m·K) at 20 °C (Plansee)." ], "watch_out": [ "Oxidation: above 400 °C in air molybdenum forms volatile MoO3 (PubChem).", "Room-temperature brittleness in as-rolled sheet: a transition above 25 °C (NASA, OCR table).", "Supply: China produced about 37 % of 2025 mine output, and China imposed export controls on molybdenum powders in February 2025 (USGS).", "No modulus, hardness, radiation or outgassing data are recorded for this profile." ], "verdict": "Molybdenum is a refractory metal that melts at 2623 °C and is mostly used to make steel and superalloys stronger. Pure metal conducts heat at 142 W/(m·K) and has a yield strength of 265 MPa in one annealed laboratory rod, but it oxidises to volatile MoO3 above 400 °C in air. The profile lacks a modulus from an accepted source, standard-product mechanical minimums and any space-environment test data.", "recipe": { "line": "Molybdenum is a single-element metal (Mo) with a body-centred cubic crystal structure (Plansee; Wikipedia). It is not found as a free metal in nature; the main ore is molybdenite (MoS2), according to Wikipedia, and the USGS says concentrate is roasted to molybdic oxide, from which metal powder is made (PubChem; USGS). In the NASA laboratory route, pressed powder electrodes were electron-beam melted into ingots, extruded, swaged and rolled.", "parts": [ { "name": "Molybdenum", "symbol": "Mo", "role": "The whole material. Atomic mass 95.94 g/mol as printed on the Plansee page.", "atoms": 1, "atomic_weight": 95.94 } ] }, "risk_groups": [ { "title": "For people", "lead": "The sources describe dust and fumes as irritants, and the aggregated ECHA data for molybdenum carry mixed hazard codes.", "points": [ { "label": "Dust and fumes", "line": "The NIOSH excerpt in PubChem says dust and fumes irritate the eyes and respiratory tract, and it lists the liver and kidneys as target organs." }, { "label": "Classification", "line": "Of 1523 company reports to the European chemicals agency, 874 said molybdenum does not meet GHS criteria. Among reports that gave codes, H228 (flammable solid) was given for 30 % and H361 (suspected of damaging fertility) for 29.5 %." } ], "level": 1, "verdict": "Mixed notifications" }, { "title": "If it fails", "lead": "These failure routes are taken from the sources. The oxidation route is a measured observation in the PubChem text, not a rate.", "points": [ { "label": "Hot air", "line": "Above 400 °C molybdenum forms a highly volatile trioxide, and above 700 °C it needs a protective coating." }, { "label": "Cold-worked sheet", "line": "Sheet cold-worked by 81 to 92 percent recrystallises fully in 1 hour at 925 °C, so it loses the strength from cold work." }, { "label": "As-rolled sheet", "line": "The NASA table gives an approximate ductile-brittle transition above 25 °C for as-rolled sheet, so it can break in a brittle way near room temperature." } ] }, { "title": "Handling and storage", "points": [ { "label": "Dust control", "line": "Keep dust and fumes away from breathing zones and eyes." }, { "label": "Hot service", "line": "Use a vacuum, an inert gas, or a protective coating when the metal is hot in air." } ] } ] }, "updated": "2026-10-25", "review": { "status": "draft", "method": "assistant", "checked_values": 13, "unreachable": 1, "caveats": 6, "note": "Values were read by an AI assistant on 2026-10-25 from the pages and PDFs named in each entry. The Plansee page is not readable by the automated check and its values were read through the web-fetch tool. Caveats: no modulus value from an accepted source; mechanical values come from one laboratory rod condition; the as-rolled transition temperature is an OCR table value; the supply shares are calculated from the USGS production table; PubChem GHS notifications are aggregated across forms." }, "sources": { "usgs-mcs2026-molybdenum": { "title": "Mineral Commodity Summaries 2026, Molybdenum (U.S. Geological Survey, February 2026)", "id": "USGS MCS 2026", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf", "year": 2026, "kind": "report", "license": "public domain (USGS)" }, "pubchem-mo": { "title": "PubChem compound record: Molybdenum (CID 23932), including ECHA C&L notifications, NIOSH and vapour pressure entries", "id": "CAS 7439-98-7, UNII 81AH48963U", "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/XML", "kind": "database", "license": "PubChem (NCBI), public domain; sections attributed to ECHA, NIOSH and others" }, "plansee-mo": { "title": "Plansee, Molybdenum material page (facts table: physical properties at 20 °C)", "url": "https://www.plansee.com/en/materials/molybdenum.html", "kind": "datasheet", "license": "Manufacturer web page (cited, not reproduced)" }, "nasa-tm-x2576": { "title": "NASA TM X-2576: Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys (Klopp and Witzke, Lewis Research Center, 1972)", "id": "NTRS 19720017873", "url": "https://ntrs.nasa.gov/api/citations/19720017873/downloads/19720017873.pdf", "year": 1972, "kind": "report", "license": "public domain (NASA)" }, "astm-b1024": { "title": "ASTM B1024/B1024M-23, Standard Specification for Isotropic Pure Molybdenum", "id": "UNS R03610", "url": "https://standards.nimonik.com/products/astm/b1024-b1024m/", "kind": "standard", "license": "Standard summary page (cited, not reproduced)" }, "astm-b387": { "title": "ASTM B387/B387M-23, Standard Specification for Molybdenum and Molybdenum Alloy Bar, Rod, and Wire", "url": "https://store.astm.org/b0387_b0387m-23.html", "kind": "standard", "license": "Standard store page (cited, not reproduced)" }, "astm-b386": { "title": "ASTM B386/B386M-25, Standard Specification for Molybdenum and Molybdenum Alloy Plate, Sheet, Strip, Foil, and Ribbon", "url": "https://store.astm.org/b0386_b0386m-25.html", "kind": "standard", "license": "Standard store page (cited, not reproduced)" }, "wikipedia-mo": { "title": "Molybdenum (Wikipedia), used for crystal structure, ore and history only", "url": "https://en.wikipedia.org/wiki/Molybdenum", "kind": "web", "license": "CC BY-SA 4.0 (cited, not reproduced)" } }, "license": "CC-BY-4.0", "url": "https://spacemushroom.com/profiles/molybdenum/" }