{
  "spore": "profile",
  "id": "stainless-420",
  "spore_version": "0.2",
  "family": "stainless-martensitic",
  "name": "Stainless steel 420",
  "abbreviation": "420",
  "role": "hardenable martensitic stainless steel for blades, bearings and wear parts",
  "category": "metals",
  "type": "steels-and-stainless",
  "summary": "AISI 420 (UNS S42000, EN 1.4021) is a martensitic stainless steel with 12.0 to 14.0 % chromium and 0.16 to 0.25 % carbon (EN composition). Annealed, its maximum hardness is 241 HB and its yield strength 51.5 ksi. Tempered at 440 °F it reaches a yield strength of 190.1 ksi and 48 HRC. Its density is 7.75 g/cm3, it is magnetic, and it resists corrosion less well than the ferritic and austenitic steels. Tempered at 1000 °F its tensile strength falls to 158.5 ksi.\n",
  "best_for": "Hardened wear parts, blades and bearing-type components that need high strength and edge retention, from one steel that reaches 48 HRC after tempering at 440 °F",
  "weakest_at": "Corrosion resistance and ductility: it resists corrosion less well than austenitic grades, and it loses strength when tempered at 1000 °F (158.5 ksi tensile)",
  "identity": {
    "formula": "Iron-chromium-carbon steel: Fe balance, Cr 12.0 to 14.0 %, C 0.16 to 0.25 % (EN 1.4021 composition)",
    "designations": [
      {
        "system": "UNS",
        "code": "S42000",
        "source": "rolledalloys-420",
        "where": "Specifications box, UNS line"
      },
      {
        "system": "EN",
        "code": "1.4021",
        "source": "rolledalloys-420",
        "where": "Specifications box, W. Nr./EN line"
      },
      {
        "system": "EN name",
        "code": "X20Cr13",
        "source": "teamedelstahl-1-4021",
        "where": "Standards and nomenclature section, page heading 1.4021 (X20Cr13 / AISI 420)"
      },
      {
        "system": "AISI",
        "code": "420",
        "source": "teamedelstahl-1-4021",
        "where": "Standards and nomenclature section, page heading 1.4021 (X20Cr13 / AISI 420)"
      },
      {
        "system": "ASTM",
        "code": "A276",
        "note": "listed specification for Type 420",
        "source": "rolledalloys-420",
        "where": "Specifications box, ASTM line"
      },
      {
        "system": "ASTM",
        "code": "A484",
        "note": "listed specification for Type 420",
        "source": "rolledalloys-420",
        "where": "Specifications box, ASTM line"
      },
      {
        "system": "AMS",
        "code": "5621",
        "source": "rolledalloys-420",
        "where": "Specifications box, AMS line"
      }
    ],
    "source": "teamedelstahl-1-4021",
    "where": "Chemical composition table, 1.4021 (X20Cr13 / AISI 420) page"
  },
  "tags": {
    "environments": [],
    "stresses": [
      "corrosion"
    ],
    "applications": [
      "mechanisms"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, 1.4021 bar (EN 10088-3)",
      "value": 7.75,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "standard": "EN 10088-3:2005",
        "temperature": "not stated"
      },
      "method": "Value printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Physical Property table, row Density",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, 1.4021 / AISI 420 (20 °C)",
      "value": 7.7,
      "bound": "exact",
      "unit": "kg/dm3",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C"
      },
      "method": "Value printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Physical properties at 20 °C table, row Density",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, Type 420 (ASTM A276)",
      "value": 0.278,
      "bound": "exact",
      "unit": "lb/in3",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temperature": "not stated"
      },
      "method": "Value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Density",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting range, Type 420",
      "value": 2650,
      "value_high": 2750,
      "bound": "range",
      "unit": "°F",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "unit_in_source": "2650 - 2750 °F"
      },
      "method": "Range printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Melting Range",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "poissons_ratio",
      "label": "Poisson's ratio, Type 420",
      "value": 0.28,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temperature": "not stated"
      },
      "method": "Value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Poisson Ratio",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Modulus of elasticity, 1.4021 bar",
      "value": 200,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "standard": "EN 10088-3:2005",
        "temperature": "not stated"
      },
      "method": "Value printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Physical Property table, row Modulus of Elasticity",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Modulus of elasticity, 1.4021 (20 °C)",
      "value": 215,
      "bound": "exact",
      "unit": "kN/mm2",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C"
      },
      "method": "Value printed in a steel supplier's material page",
      "status": "ground",
      "note": "The other two sources give 200 GPa (Aalco) and 31.2 x 10^6 psi, which is about 215 GPa; the 200 GPa figure is a separate row.",
      "source": "teamedelstahl-1-4021",
      "where": "Mechanical properties at 20 °C table, row Modulus of elasticity",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Modulus of elasticity, Type 420 (68 °F)",
      "value": 31.2,
      "bound": "exact",
      "unit": "10^6 psi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temperature": "68 °F"
      },
      "method": "Value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Modulus of Elasticity (68°F)",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, 1.4021 bar",
      "value": 24.9,
      "bound": "exact",
      "unit": "W/(m·K)",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "temperature": "not stated"
      },
      "method": "Value printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Physical Property table, row Thermal Conductivity",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, 1.4021 (20 °C)",
      "value": 30,
      "bound": "exact",
      "unit": "W/(m·K)",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C"
      },
      "method": "Value printed in a steel supplier's material page",
      "status": "ground",
      "note": "Two sources differ: 24.9 W/(m·K) (Aalco, temperature not stated) and 30 W/(m·K) at 20 °C (teamedelstahl). Both are kept with their conditions.",
      "source": "teamedelstahl-1-4021",
      "where": "Physical properties at 20 °C table, row Thermal conductivity",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, Type 420 (212 °F)",
      "value": 14.4,
      "bound": "exact",
      "unit": "BTU/(hr·ft·°F)",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temperature": "212 °F"
      },
      "method": "Value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Thermal Conductivity (212°F)",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "cte",
      "label": "Coefficient of thermal expansion, 1.4021 bar (0 to 100 °C)",
      "value": 10.3,
      "bound": "exact",
      "unit": "10^-6/K",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "temperature_range": "not stated in the Aalco table"
      },
      "method": "Value printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Physical Property table, row Thermal Expansion",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "cte",
      "label": "Coefficient of thermal expansion, Type 420 (68 to 212 °F)",
      "value": 5.833,
      "bound": "exact",
      "unit": "µin/in·°F",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temperature": "68 to 212 °F"
      },
      "method": "Value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Coefficient of Thermal Expansion (68°F - 212°F)",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Specific heat capacity, 1.4021 (20 °C)",
      "value": 460,
      "bound": "exact",
      "unit": "J/(kg·K)",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C"
      },
      "method": "Value printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Physical properties at 20 °C table, row Specific heat capacity",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "label": "Electrical resistivity, 1.4021 bar",
      "value": 0.55,
      "bound": "exact",
      "unit": "µΩ·m",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "unit_in_source": "x10^-6 Ω.m",
        "temperature": "not stated"
      },
      "method": "Value printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Physical Property table, row Electrical Resistivity",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "label": "Electrical resistivity, 1.4021 (20 °C)",
      "value": 0.6,
      "bound": "exact",
      "unit": "Ω·mm2/m",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C"
      },
      "method": "Value printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Physical properties at 20 °C table, row Electrical resistance",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "label": "Electrical resistivity, Type 420",
      "value": 25.6,
      "bound": "exact",
      "unit": "µΩ·in",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temperature": "not stated"
      },
      "method": "Value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Physical Properties, row Electrical Resistivity",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "Yield strength 0.2 % offset, Type 420 annealed (Condition A)",
      "value": 51.5,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "annealed (Condition A, ASTM A276)",
        "measure": "0.2 % yield strength"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row Annealed, column 0.2% Yield Strength",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "Yield strength 0.2 % offset, Type 420 tempered at 440 °F",
      "value": 190.1,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "tempered at 440 °F",
        "measure": "0.2 % yield strength"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row 440, column 0.2% Yield Strength",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "Yield strength 0.2 % offset, Type 420 tempered at 1000 °F",
      "value": 137.9,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "tempered at 1000 °F",
        "measure": "0.2 % yield strength"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "note": "Over-tempering: the same table gives 36 HRC at this temper, against 48 HRC at 440 °F.",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row 1000, column 0.2% Yield Strength",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "Proof stress Rp0.2, 1.4021 bar up to 160 mm",
      "value": 500,
      "value_high": 600,
      "bound": "range",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "standard": "EN 10088-3:2005",
        "temper": "not stated"
      },
      "method": "Range printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Mechanical Property table under Spec EN 10088-3:2005, row Proof Stress",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "yield_strength",
      "label": "Yield strength Rp0.2, 1.4021 (20 °C) lower limit",
      "value": 460,
      "bound": "lower",
      "unit": "N/mm2",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C",
        "temper": "not stated"
      },
      "method": "Minimum value printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Mechanical properties at 20 °C table, row Yield point Rp0.2",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, Type 420 annealed (Condition A)",
      "value": 85.8,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "annealed (Condition A, ASTM A276)"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row Annealed, column Ultimate Tensile Strength",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, Type 420 tempered at 440 °F",
      "value": 255.2,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "tempered at 440 °F"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row 440, column Ultimate Tensile Strength",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, Type 420 tempered at 1000 °F",
      "value": 158.5,
      "bound": "exact",
      "unit": "ksi",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "tempered at 1000 °F"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row 1000, column Ultimate Tensile Strength",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength Rm, 1.4021 bar up to 160 mm",
      "value": 700,
      "value_high": 950,
      "bound": "range",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "standard": "EN 10088-3:2005",
        "temper": "not stated"
      },
      "method": "Range printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Mechanical Property table under Spec EN 10088-3:2005, row Tensile Strength",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength Rm, 1.4021 (20 °C)",
      "value": 750,
      "value_high": 850,
      "bound": "range",
      "unit": "N/mm2",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C",
        "temper": "not stated"
      },
      "method": "Range printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Mechanical properties at 20 °C table, row Tensile strength Rm",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation A, 1.4021 bar up to 160 mm",
      "value": 12,
      "value_high": 13,
      "bound": "range",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420) bar, up to 160 mm",
        "standard": "EN 10088-3:2005",
        "temper": "not stated"
      },
      "method": "Range printed in a stockholder datasheet",
      "status": "ground",
      "source": "aalco-1-4021",
      "where": "Mechanical Property table under Spec EN 10088-3:2005, row Elongation A",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elongation",
      "label": "Elongation A5.65, 1.4021 (20 °C) lower limit",
      "value": 12,
      "bound": "lower",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C",
        "temper": "not stated"
      },
      "method": "Minimum value printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Mechanical properties at 20 °C table, row Elongation A5,65",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "hardness_brinell",
      "label": "Hardness Brinell maximum, Type 420 annealed (Condition A)",
      "value": 241,
      "bound": "upper",
      "unit": "HB",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "annealed (Condition A, ASTM A276)"
      },
      "method": "Maximum value printed in a mill datasheet",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Mechanical Properties, row Hardness MAX, Brinell (Condition A footnote)",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "hardness_brinell",
      "label": "Hardness Brinell maximum, 1.4021 (20 °C)",
      "value": 230,
      "bound": "upper",
      "unit": "HB",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (X20Cr13 / AISI 420)",
        "temperature": "20 °C",
        "temper": "not stated"
      },
      "method": "Maximum value printed in a steel supplier's material page",
      "status": "ground",
      "source": "teamedelstahl-1-4021",
      "where": "Mechanical properties at 20 °C table, row Hardness HB",
      "source_detail": {
        "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
        "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
        "kind": "datasheet",
        "license": "Supplier material page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "hardness_rockwell_c",
      "label": "Hardness Rockwell C, Type 420 tempered at 440 °F",
      "value": 48,
      "bound": "exact",
      "unit": "HRC",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "tempered at 440 °F"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row 440, column Rockwell Hardness HRC",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "hardness_rockwell_c",
      "label": "Hardness Rockwell C, Type 420 tempered at 1000 °F",
      "value": 36,
      "bound": "exact",
      "unit": "HRC",
      "scope": "material",
      "conditions": {
        "grade": "Type 420, UNS S42000",
        "temper": "tempered at 1000 °F"
      },
      "method": "Value printed in a mill datasheet, tempered-condition table",
      "status": "ground",
      "source": "rolledalloys-420",
      "where": "Tempered Condition Properties table, row 1000, column Rockwell Hardness HRC",
      "source_detail": {
        "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
        "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
        "year": 2022,
        "kind": "datasheet",
        "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Scaling resistance limit, continuous (1.4021)",
      "value": 675,
      "bound": "upper",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "grade": "1.4021 (420)",
        "basis": "scaling resistance, continuous",
        "intermittent_limit": "760 °C",
        "note_in_source": "use above the tempering temperature is not recommended if mechanical properties must be kept"
      },
      "method": "Value printed in a stockholder datasheet, corrosion resistance section",
      "status": "ground",
      "note": "A scaling limit, not a structural service limit. The Aalco page says mechanical properties fall above the tempering temperature.",
      "source": "aalco-1-4021",
      "where": "Corrosion Resistance section, Heat resistance paragraph",
      "source_detail": {
        "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
        "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
        "kind": "datasheet",
        "license": "Stockholder datasheet (cited, not reproduced)"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Air and humid atmospheres",
      "headline": "Martensitic steels resist corrosion less well than ferritic and austenitic grades because their chromium is low.",
      "effect": "Wikipedia says martensitic stainless steels are not as corrosion-resistant as ferritic and austenitic grades due to their low chromium content, and lists Type 420 as a representative grade. Rolled Alloys says 420 offers corrosion resistance comparable to that of Type 410.",
      "rating": "moderate",
      "conditions": {
        "basis": "general comparison; no corrosion rate or test environment given in the sources"
      },
      "source": "wikipedia-stainless",
      "where": "Families, Martensitic section"
    },
    {
      "environment": "Hardened condition",
      "headline": "Maximum corrosion resistance is reached in the fully hardened condition, not the annealed one.",
      "effect": "Aalco states that maximum corrosion resistance is achieved in the hardened condition, and the Rolled Alloys sheet describes 420 as similar to 410 in corrosion resistance. No corrosion rate is given.",
      "rating": "moderate",
      "conditions": {
        "basis": "qualitative statement; no test environment given"
      },
      "source": "aalco-1-4021",
      "where": "Corrosion Resistance section"
    },
    {
      "environment": "High-temperature scaling in air",
      "headline": "420 scales in air at high temperature, with a continuous limit of 675 °C.",
      "effect": "Aalco gives fair scaling resistance up to 760 °C intermittently and 675 °C continuously, and says use above the tempering temperature is not recommended if mechanical properties must be kept.",
      "rating": "moderate",
      "conditions": {
        "basis": "scaling resistance in air; no weight-gain or rate values given"
      },
      "source": "aalco-1-4021",
      "where": "Corrosion Resistance section, Heat resistance paragraph"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "Generic stainless steel SDS (Parker Steel, Metric Metal), not a 420-specific sheet: solid metal products are generally articles and not hazardous materials under the OSHA Hazard Communication Standard. Small chips, fines and dust may ignite readily, and hazardous elements can be released during cutting, grinding and welding. Do not breathe dust or fume.",
        "ghs": [],
        "source": "metric-sds",
        "where": "Section 2 Hazards Identification, General Hazard Statement and Hazard Statements; generic SDS, GHS classes not applied to 420 here"
      },
      {
        "text": "Welding, torch cutting or grinding of stainless steel can generate hexavalent chromium. The SDS notes that chromium metal in the zero valence state does not present an unusual health hazard.",
        "ghs": [],
        "source": "metric-sds",
        "where": "Asterisked footnote to the composition table on chromium metal"
      }
    ],
    "failure_risks": [
      {
        "mode": "Loss of strength from over-tempering",
        "trigger": "Tempering or service at 1000 °F (538 °C)",
        "consequence": "The Rolled Alloys table gives 158.5 ksi tensile and 137.9 ksi yield at 1000 °F, against 255.2 ksi tensile at 440 °F, and 36 HRC against 48 HRC. Aalco also warns of strength loss from over-tempering at elevated temperature.",
        "severity": "high",
        "source": "rolledalloys-420",
        "where": "Tempered Condition Properties table, rows 440 and 1000; Aalco Temperature notes"
      },
      {
        "mode": "Brittleness at sub-zero temperature",
        "trigger": "Service below zero degrees Celsius",
        "consequence": "Aalco says the useful temperature range is limited by loss of ductility below zero.",
        "severity": "moderate",
        "source": "aalco-1-4021",
        "where": "Operating range paragraph, Temperature notes"
      },
      {
        "mode": "Cracking during hot working",
        "trigger": "Hot working below 1700 °F (927 °C)",
        "consequence": "Aalco says hot work below 1700 °F may cause cracking; work should start after uniform heating to 2100 to 2250 °F (1149 to 1232 °C).",
        "severity": "moderate",
        "source": "aalco-1-4021",
        "where": "Hot working paragraph, Temperature notes"
      },
      {
        "mode": "Weld joint strength",
        "trigger": "Welding high-strength joints without post-weld heat treatment",
        "consequence": "Aalco recommends post-weld hardening and tempering for high-strength joints, with preheat at 150 to 320 °C and post-heat at 610 to 760 °C.",
        "severity": "low",
        "source": "aalco-1-4021",
        "where": "Weldability section"
      }
    ],
    "side_effects": [
      {
        "text": "420 is magnetic, in both the annealed and hardened condition, so it cannot be used where a nonmagnetic material is required.",
        "affects": "Magnetic response of parts and assemblies",
        "source": "wikipedia-stainless",
        "where": "Properties, Magnetism section; Families, Martensitic section"
      }
    ],
    "handling": [
      {
        "text": "Specify the temper with the order: strength and hardness follow the tempering temperature, from 255.2 ksi tensile at 440 °F to 158.5 ksi at 1000 °F (Rolled Alloys table).",
        "source": "rolledalloys-420",
        "where": "Tempered Condition Properties table"
      },
      {
        "text": "Harden and temper after fabrication. The supplier's thermal-treatment table gives hardening at 950 to 1050 °C with oil, polymer or air cooling, and tempering at 600 to 700 °C or 650 to 750 °C.",
        "source": "teamedelstahl-1-4021",
        "where": "Thermal treatment table"
      }
    ],
    "mitigations": [
      {
        "text": "Ventilate or enclose cutting, grinding and welding to limit dust and fume, as the generic stainless SDS advises.",
        "source": "metric-sds",
        "where": "Engineering controls paragraph in the handling section"
      }
    ]
  },
  "uses": [
    {
      "application": "mechanisms",
      "device": "Bearings and industrial chains",
      "example": "Rolled Alloys lists industrial chains and bearings among the applications of Type 420, which it says is used for high strength, high wear resistance or good edge retention.",
      "source": "rolledalloys-420",
      "where": "Applications list"
    },
    {
      "application": "mechanisms",
      "device": "Pumps and valves",
      "example": "Rolled Alloys lists pumps and valves, and plastic injection moulds and dies, among the applications of Type 420.",
      "source": "rolledalloys-420",
      "where": "Applications list"
    }
  ],
  "supply": [
    {
      "subject": "Chromium (mine production, the alloying element in 420)",
      "producers": [
        {
          "country": "South Africa",
          "share_percent": 45.1,
          "year": 2025
        },
        {
          "country": "Turkey",
          "share_percent": 17.6,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 13.7,
          "year": 2025
        }
      ],
      "critical_lists": [],
      "recycling": "USGS: in 2025 recycled chromium contained in stainless-steel scrap receipts accounted for 21 % of apparent consumption. The United States imported 79 % of its apparent consumption (2025e net import reliance).",
      "substitutes": [
        "USGS: chromium has no substitute in stainless steel, the leading end use, or in superalloys. Chromium-containing scrap can substitute for ferrochromium in some metallurgical uses."
      ],
      "source": "usgs-mcs2026-chromium",
      "where": "World Mine Production and Reserves table, 2025e column (world total 51,000 thousand t, gross weight: South Africa 23,000, Turkey 9,000, Kazakhstan 7,000); shares calculated by Space Mushroom from those values; Recycling; Substitutes; Domestic Production and Use"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Rolled Alloys data sheet 420 (UNS S42000, W. Nr./EN 1.4021), 2022",
      "type": "datasheet",
      "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
      "year": 2022
    },
    {
      "title": "Aalco datasheet, Stainless Steel 1.4021 (420) Bar",
      "type": "datasheet",
      "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx"
    },
    {
      "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
      "type": "datasheet",
      "url": "https://www.teamedelstahl.de/en/materials/1-4021/"
    },
    {
      "title": "Righton Blackburns datasheet, Stainless Steel 1.4021 (420) Bar",
      "type": "datasheet",
      "url": "https://www.rightonblackburns.co.uk/datasheets/view/stainless-steel-1-4021-420-bar"
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Chromium",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf",
      "year": 2026
    },
    {
      "title": "Metric Metal safety data sheet, Stainless Steels (Parker Steel, issue 2/1/2016)",
      "type": "sds",
      "url": "https://www.metricmetal.com/wp-content/uploads/2018/08/G-SDS-Stainless-Steel.pdf",
      "year": 2016
    },
    {
      "title": "Wikipedia: Martensitic stainless steel",
      "type": "database",
      "url": "https://en.wikipedia.org/wiki/Martensitic_stainless_steel"
    },
    {
      "title": "Wikipedia: Stainless steel",
      "type": "database",
      "url": "https://en.wikipedia.org/wiki/Stainless_steel"
    }
  ],
  "gaps": [
    "Atomic weights for the recipe parts (Fe, Cr, C) were not read from a fetched page, so the recipe gives weight shares only.",
    "No primary ASTM A276 or EN 10088-3 table was opened; the mechanical values come from a stockholder page (Aalco), a supplier page (teamedelstahl) and a mill sheet (Rolled Alloys), each for a different temper or product size.",
    "The Aalco page describes its bar as a sulphur-enhanced machining grade. The sulphur figure (0.030 % maximum) is the same as the other sources, but the free-machining claim was not checked against a second source.",
    "Heat-treated hardness for 1.4021 (quench plus temper) in HRC was not found in a 1.4021-specific source. The 45 to 50 HRC and 52 to 55 HRC figures seen on other pages are for a different grade (420J1) or are not tied to a grade, so they are not used.",
    "Tensile and yield values from the Saky Steel SUS 420 table (650 MPa max) conflict with the EN figures (700 to 950 MPa) and are for a JIS grade with a different carbon range; they are not used.",
    "Atlas Quality Management, makeitfrom.com (403), the Combined Metals PDF and the Timken SDS could not be read in this run.",
    "No ISO 9223 corrosion rate, salt-spray result or pitting test for 420 was found in a fetched source.",
    "No cryogenic, impact (Charpy) or fatigue values for 420 were found in a fetched source.",
    "Radiation, outgassing, atomic oxygen and cold-welding data for 420 in vacuum were not looked up.",
    "The USGS 2026 chromium summary does not state whether chromium is on the U.S. critical minerals list, so critical_lists is empty.",
    "Hardness is recorded as hardness_brinell and hardness_rockwell_c because the canonical file has no hardness entry; these names are not in the canonical list.",
    "No PubChem or Wikipedia GHS record for the alloy was opened; the PubChem chromium page was blocked by a CAPTCHA."
  ],
  "story": {
    "why": "AISI 420 (UNS S42000, EN 1.4021) is a martensitic stainless steel with 12.0 to 14.0 % chromium and 0.16 to 0.25 % carbon. The carbon lets it be hardened, so it reaches about 48 HRC after tempering at 440 °F (Rolled Alloys), while annealed it is soft, at most 241 HB. Its density is 7.75 g/cm3, and it is magnetic. It is chosen where a steel must be hard and wear-resistant and still stainless enough for blades, chains, bearings and valves. Its weak points are corrosion resistance, which is lower than that of austenitic steels, and strength loss if it is over-tempered.",
    "uses": [
      {
        "where": "Bearings and chains",
        "line": "Rolled Alloys lists industrial chains and bearings among the applications of Type 420, which is used for high strength, high wear resistance or good edge retention."
      },
      {
        "where": "Pumps and valves",
        "line": "Rolled Alloys lists pumps and valves, and plastic injection moulds and dies, among the applications of Type 420."
      }
    ],
    "can_do": [
      {
        "label": "Carry load when hard",
        "line": "Tempered at 440 °F, Type 420 has a tensile strength of 255.2 ksi and a yield strength of 190.1 ksi (Rolled Alloys tempered-condition table).",
        "benchmark": "ultimate_tensile_strength",
        "scope": "material",
        "value": "255.2 ksi tensile"
      },
      {
        "label": "Stay hard",
        "line": "The same tempered condition gives 48 HRC. Tempering at 1000 °F drops this to 36 HRC.",
        "benchmark": "hardness_rockwell_c",
        "scope": "material",
        "value": "48 HRC"
      },
      {
        "label": "Soft to form",
        "line": "Annealed (Condition A), the maximum hardness is 241 HB, and the yield strength is 51.5 ksi.",
        "benchmark": "hardness_brinell",
        "scope": "material",
        "value": "241 HB maximum"
      },
      {
        "label": "Weight",
        "line": "Density is 7.75 g/cm3 in the Aalco datasheet, and 7.7 kg/dm3 at 20 °C in the teamedelstahl page.",
        "benchmark": "density",
        "scope": "material",
        "value": "7.75 g/cm3"
      },
      {
        "label": "Heat to 675 °C",
        "line": "Aalco gives a scaling limit of 675 °C continuous and 760 °C intermittent. This is a scaling limit; above the tempering temperature the mechanical properties fall.",
        "benchmark": "max_service_temp",
        "scope": "material",
        "value": "675 °C continuous"
      }
    ],
    "compare": "Among the stainless steels, 420 trades corrosion resistance for hardness: Wikipedia says martensitic steels are less corrosion-resistant than ferritic and austenitic grades. Its density of 7.75 g/cm3 (Aalco) is close to the value of 7.7 kg/dm3 given by teamedelstahl for the same grade. The compare rows use the figures printed by the sources, not a ranking of different alloys.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Thermal conductivity",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      },
      {
        "label": "Thermal expansion",
        "benchmark": "cte",
        "scope": "material"
      }
    ],
    "handling": [
      "Specify the temper, because strength and hardness follow the tempering temperature (Rolled Alloys table).",
      "Harden and temper after fabrication, following the thermal-treatment table (hardening 950 to 1050 °C, then tempering).",
      "Keep tempering below 1000 °F for useful strength, since 1000 °F tempering drops tensile strength to 158.5 ksi.",
      "Ventilate cutting, grinding and welding to limit dust and fume."
    ],
    "good_for": [
      "Hard, wear-resistant parts: 48 HRC after tempering at 440 °F (Rolled Alloys).",
      "Stainless service with a magnetic response: 420 is magnetic in both conditions (Wikipedia).",
      "Scaling in air up to 675 °C continuous (Aalco)."
    ],
    "watch_out": [
      "Corrosion: lower than that of austenitic grades, and best in the hardened condition (Aalco, Wikipedia).",
      "Over-tempering at 1000 °F drops tensile strength to 158.5 ksi.",
      "Sub-zero ductility is lost (Aalco), so brittle failure is a risk in cold service.",
      "Sources differ on thermal conductivity (24.9 W/(m·K) against 30 W/(m·K)) and modulus (200 GPa against 215 GPa)."
    ],
    "verdict": "AISI 420 (UNS S42000, EN 1.4021) is a hardenable stainless steel for blades, chains, bearings and valves. It reaches 48 HRC when tempered at 440 °F, weighs 7.75 g/cm3 and is magnetic. It resists corrosion less well than austenitic steels and loses strength when over-tempered. This profile lacks a 1.4021-specific corrosion rate, impact values and vacuum data.",
    "recipe": {
      "line": "Martensitic stainless steel of iron with about 12 to 14 % chromium and 0.16 to 0.25 % carbon (EN 1.4021 composition). The steel is hot-worked after uniform heating to 1149 to 1232 °C (Aalco), then hardened and tempered (teamedelstahl).",
      "parts": [
        {
          "name": "Iron",
          "symbol": "Fe",
          "role": "Matrix of the steel"
        },
        {
          "name": "Chromium",
          "symbol": "Cr",
          "role": "Gives the steel its stainless character; low chromium makes it less corrosion-resistant than ferritic and austenitic grades (Wikipedia)"
        },
        {
          "name": "Carbon",
          "symbol": "C",
          "role": "Makes the steel hardenable; gives higher heat-treated strength at some cost in ductility (Rolled Alloys)"
        },
        {
          "name": "Manganese",
          "symbol": "Mn",
          "role": "Maximum allowed in the composition (teamedelstahl composition table)"
        },
        {
          "name": "Silicon",
          "symbol": "Si",
          "role": "Maximum allowed in the composition (teamedelstahl composition table)"
        },
        {
          "name": "Sulphur",
          "symbol": "S",
          "role": "Limit on the impurity; Aalco describes its bar as sulphur-enhanced for machining"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The sources describe a generic stainless steel SDS for solid stock, and the risk comes from dust, fume and processing rather than from the solid.",
        "points": [
          {
            "label": "Solid stock",
            "line": "A generic stainless steel SDS says solid metal articles are generally not hazardous materials under the OSHA Hazard Communication Standard. Small chips, fines and dust may ignite readily."
          },
          {
            "label": "Processing",
            "line": "Cutting, grinding and welding can release hazardous elements, and welding or grinding can generate hexavalent chromium. Ventilation is the control the SDS names."
          }
        ],
        "level": 1,
        "verdict": "Low for solid stock, higher for dust and fume"
      },
      {
        "title": "If it fails",
        "lead": "The failure routes in the sources are about temper and temperature, not about a single corrosion rate.",
        "points": [
          {
            "label": "Over-tempering",
            "line": "Tempered at 1000 °F, 420 falls to 158.5 ksi tensile and 36 HRC, against 255.2 ksi and 48 HRC at 440 °F (Rolled Alloys)."
          },
          {
            "label": "Sub-zero service",
            "line": "Aalco says ductility is lost below zero, which limits the useful range."
          },
          {
            "label": "Corrosion",
            "line": "Wikipedia says martensitic steels resist corrosion less well than ferritic and austenitic grades. Aalco says maximum corrosion resistance is reached in the hardened condition."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Keep the temper in view",
            "line": "Strength and hardness follow the tempering temperature. The order should name the temper."
          },
          {
            "label": "Welds",
            "line": "Aalco recommends preheat at 150 to 320 °C and post-heat at 610 to 760 °C for high-strength joints."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-25",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 37,
    "unreachable": 4,
    "caveats": 6,
    "note": "Values were read by an AI assistant on 2026-10-25 from the pages and PDFs named in each entry. The Rolled Alloys sheet was read from the PDF text. Unreachable in this run: Atlas Quality Management PDF, makeitfrom.com (403), Combined Metals PDF (image-only), Timken SDS (HTML). Caveats: values differ between sources and tempers; the Rolled Alloys tempering table uses ksi; the Metric Metal SDS is generic stainless and not 420-specific; the Aalco bar is sulphur-enhanced; hardness names are not canonical."
  },
  "sources": {
    "rolledalloys-420": {
      "title": "Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22",
      "url": "https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf",
      "year": 2022,
      "kind": "datasheet",
      "license": "Manufacturer data sheet, no warranty (cited, not reproduced)"
    },
    "aalco-1-4021": {
      "title": "Aalco Stainless Steel 1.4021 (420) Bar datasheet",
      "url": "https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx",
      "kind": "datasheet",
      "license": "Stockholder datasheet (cited, not reproduced)"
    },
    "teamedelstahl-1-4021": {
      "title": "teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)",
      "url": "https://www.teamedelstahl.de/en/materials/1-4021/",
      "kind": "datasheet",
      "license": "Supplier material page (cited, not reproduced)"
    },
    "rightonblackburns-1-4021": {
      "title": "Righton Blackburns datasheet, Stainless Steel 1.4021 (420) Bar",
      "url": "https://www.rightonblackburns.co.uk/datasheets/view/stainless-steel-1-4021-420-bar",
      "kind": "datasheet",
      "license": "Stockholder datasheet (cited, not reproduced)"
    },
    "usgs-mcs2026-chromium": {
      "title": "Mineral Commodity Summaries 2026, Chromium",
      "id": "USGS MCS 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "metric-sds": {
      "title": "Metric Metal safety data sheet, Stainless Steels (Parker Steel), issue 2/1/2016",
      "url": "https://www.metricmetal.com/wp-content/uploads/2018/08/G-SDS-Stainless-Steel.pdf",
      "year": 2016,
      "kind": "datasheet",
      "license": "Manufacturer safety data sheet (cited, not reproduced)"
    },
    "wikipedia-martensitic": {
      "title": "Wikipedia: Martensitic stainless steel",
      "url": "https://en.wikipedia.org/wiki/Martensitic_stainless_steel",
      "kind": "web",
      "license": "CC BY-SA 4.0 (cited, not reproduced)"
    },
    "wikipedia-stainless": {
      "title": "Wikipedia: Stainless steel (Families and Properties sections)",
      "url": "https://en.wikipedia.org/wiki/Stainless_steel",
      "kind": "web",
      "license": "CC BY-SA 4.0 (cited, not reproduced)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/stainless-420/"
}