Alloy steel AISI 4340 (nickel-chromium-molybdenum) 4340 (UNS G43400)

spore: profile
id: steel-4340
spore_version: '0.2'
family: carbon-and-alloy-steels
name: Alloy steel AISI 4340 (nickel-chromium-molybdenum)
abbreviation: 4340 (UNS G43400)
role: structural alloy
category: metals
type: steels-and-stainless
summary: AISI 4340 (UNS G43400) is a nickel-chromium-molybdenum low-alloy steel. Its composition ranges are 0.38 to 0.43 percent carbon, 1.65 to 2.00 percent nickel, 0.70 to 0.90 percent chromium and 0.20 to 0.30 percent molybdenum (eFunda). Quenched and tempered to condition U (100 mm ruling section), its minimum yield strength is 740 MPa, and the supplier says it has higher tensile and yield strength than 4140 (voestalpine).
best_for: Large sections that need high tensile strength and toughness after quenching and tempering, such as aircraft landing gear, gears and shafts (voestalpine, Saky Steel).
weakest_at: 'Toughness at the highest strength levels: the minimum Charpy impact energy falls from 42 J at condition U to 9 J at condition Z (voestalpine). No corrosion data were read for this grade.'
identity:
  formula: 'Fe balance; 0.38 to 0.43 C, 0.60 to 0.80 Mn, 0.15 to 0.30 Si, 0.70 to 0.90 Cr, 1.65 to 2.00 Ni, 0.20 to 0.30 Mo, 0.035 max P, 0.04 max S (wt%, composition ranges as printed by eFunda). The voestalpine datasheet prints single values under chemical analysis: C 0.43, Si 0.3, Mn 0.8, Ni 2.00, Cr 0.9, Mo 0.3, S 0.025, P 0.035.'
  source: efunda-4340
  where: Composition table, Element and Weight % rows C to Mo (eFunda); the voestalpine chemical analysis row is printed in the formula text
  designations:
    - system: UNS
      code: G43400
      source: voestalpine-4340
      where: NEAREST STANDARDS table, UNS column
    - system: AISI
      code: '4340'
      source: voestalpine-4340
      where: NEAREST STANDARDS table, AISI column
    - system: SAE
      code: '4340'
      source: wiki-4340-steel
      where: Reference list, title of SAE AMS6414M, printed (SAE 4340)
    - system: AMS
      code: '6414'
      source: efunda-4340
      where: Designations, United States list, AMS 6414
    - system: AMS
      code: 6414A
      source: efunda-4340
      where: Designations, United States list, AMS 6414A
    - system: AMS
      code: '6415'
      source: efunda-4340
      where: Designations, United States list, AMS 6415
    - system: AMS
      code: 6415G
      source: efunda-4340
      where: Designations, United States list, AMS 6415G
    - system: MIL
      code: MIL-S-16974
      source: efunda-4340
      where: Designations, United States list, MIL SPEC MIL-S-16974
    - system: ASTM
      code: A322
      source: efunda-4340
      where: Designations, United States list, ASTM A322
    - system: ASTM
      code: A331
      source: efunda-4340
      where: Designations, United States list, ASTM A331
    - system: ASTM
      code: A505
      source: efunda-4340
      where: Designations, United States list, ASTM A505
    - system: ASTM
      code: A519
      source: efunda-4340
      where: Designations, United States list, ASTM A519
    - system: ASTM
      code: A547
      source: efunda-4340
      where: Designations, United States list, ASTM A547
    - system: ASTM
      code: A646
      source: efunda-4340
      where: Designations, United States list, ASTM A646
    - system: SAE
      code: J404
      source: efunda-4340
      where: Designations, United States list, SAE J404
    - system: SAE
      code: J412
      source: efunda-4340
      where: Designations, United States list, SAE J412
    - system: SAE
      code: J770
      source: efunda-4340
      where: Designations, United States list, SAE J770
    - system: JIS
      code: SNCM 8
      source: efunda-4340
      where: 'Designations, Japan: JIS SNCM 8'
    - system: BS
      code: 817M40
      source: efunda-4340
      where: 'Designations, United Kingdom: B.S. 817 M 40'
    - system: BS
      code: EN24
      note: nearest equivalent
      source: voestalpine-4340
      where: NEAREST STANDARDS table, BS column
    - system: EN
      code: '1.6565'
      note: nearest equivalent
      source: voestalpine-4340
      where: NEAREST STANDARDS table, DIN column, printed 1.6565 / 40NiCrMo6
    - system: EN name
      code: 40NiCrMo6
      note: nearest equivalent
      source: voestalpine-4340
      where: NEAREST STANDARDS table, DIN column, printed 1.6565 / 40NiCrMo6
    - system: EN
      code: '1.6582'
      note: nearest equivalent
      source: saky-4340-flatbar
      where: 'Product description: commonly known as 34CrNiMo6, 1.6582, or 817M40 in international standards'
    - system: EN name
      code: 34CrNiMo6
      note: nearest equivalent
      source: saky-4340-flatbar
      where: 'Product description: commonly known as 34CrNiMo6, 1.6582, or 817M40 in international standards'
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - mechanisms
properties:
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition T
    value: 665
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition T
      section: limiting ruling section 150 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column T, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition T
    value: 850
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition T
      section: limiting ruling section 150 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, range
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column T, row Tensile Rm (Mpa)
    value_high: 1000
    bound: range
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition T
    value: 13
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: quenched and tempered to condition T
      section: limiting ruling section 150 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column T, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition T
    value: 35
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: quenched and tempered to condition T
      section: limiting ruling section 150 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column T, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition T
    value: 248
    unit: HB
    scope: material
    conditions:
      condition: quenched and tempered to condition T
      section: limiting ruling section 150 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column T, row Hardness (HB)
    value_high: 302
    bound: range
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition U
    value: 740
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition U
      section: limiting ruling section 100 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column U, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition U
    value: 930
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition U
      section: limiting ruling section 100 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, range
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column U, row Tensile Rm (Mpa)
    value_high: 1080
    bound: range
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition U
    value: 12
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: quenched and tempered to condition U
      section: limiting ruling section 100 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column U, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition U
    value: 42
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: quenched and tempered to condition U
      section: limiting ruling section 100 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column U, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition U
    value: 269
    unit: HB
    scope: material
    conditions:
      condition: quenched and tempered to condition U
      section: limiting ruling section 100 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column U, row Hardness (HB)
    value_high: 331
    bound: range
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition V
    value: 835
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition V
      section: limiting ruling section 63 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column V, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition V
    value: 1000
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition V
      section: limiting ruling section 63 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, range
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column V, row Tensile Rm (Mpa)
    value_high: 1150
    bound: range
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition V
    value: 12
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: quenched and tempered to condition V
      section: limiting ruling section 63 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column V, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition V
    value: 42
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: quenched and tempered to condition V
      section: limiting ruling section 63 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column V, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition V
    value: 293
    unit: HB
    scope: material
    conditions:
      condition: quenched and tempered to condition V
      section: limiting ruling section 63 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column V, row Hardness (HB)
    value_high: 352
    bound: range
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition W
    value: 925
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition W
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column W, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition W
    value: 1080
    unit: MPa
    scope: material
    conditions:
      condition: quenched and tempered to condition W
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, range
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column W, row Tensile Rm (Mpa)
    value_high: 1230
    bound: range
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition W
    value: 11
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: quenched and tempered to condition W
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column W, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition W
    value: 35
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: quenched and tempered to condition W
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column W, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition W
    value: 311
    unit: HB
    scope: material
    conditions:
      condition: quenched and tempered to condition W
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column W, row Hardness (HB)
    value_high: 375
    bound: range
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition X*
    value: 1005
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered to condition X* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column X*, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition X*
    value: 1150
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered to condition X* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, range
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column X*, row Tensile Rm (Mpa)
    value_high: 1300
    bound: range
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition X*
    value: 10
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: 'quenched and tempered to condition X* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column X*, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition X*
    value: 28
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: 'quenched and tempered to condition X* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column X*, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition X*
    value: 341
    unit: HB
    scope: material
    conditions:
      condition: 'quenched and tempered to condition X* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column X*, row Hardness (HB)
    value_high: 401
    bound: range
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition Y*
    value: 1080
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Y* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Y*, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition Y*
    value: 1230
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Y* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, range
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Y*, row Tensile Rm (Mpa)
    value_high: 1380
    bound: range
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition Y*
    value: 10
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Y* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Y*, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition Y*
    value: 20
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Y* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Y*, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition Y*
    value: 363
    unit: HB
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Y* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Y*, row Hardness (HB)
    value_high: 429
    bound: range
  - benchmark: yield_strength
    label: Yield strength (Rp0.2 minimum), quenched and tempered, condition Z*
    value: 1125
    bound: lower
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Z* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rp0.2, minimum
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Z*, row Yield Strength (Rp 0.2 (Mpa))
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Rm), quenched and tempered, condition Z*
    value: 1550
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Z* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      strength_type: Rm, printed as greater than
      unit_in_source: Mpa
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Z*, row Tensile Rm (Mpa)
    bound: lower
  - benchmark: elongation
    label: Elongation (A5) minimum, quenched and tempered, condition Z*
    value: 5
    bound: lower
    unit: '%'
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Z* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      gauge: A5
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Z*, row Elongation (A5 %)
  - benchmark: impact_energy
    label: Charpy impact energy (minimum), quenched and tempered, condition Z*
    value: 9
    bound: lower
    unit: J
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Z* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      test: Charpy impact
      test_temperature: not printed
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Z*, row Charpy Impact (J)
  - benchmark: hardness_brinell
    label: Hardness (HB), quenched and tempered, condition Z*
    value: 444
    unit: HB
    scope: material
    conditions:
      condition: 'quenched and tempered to condition Z* (asterisked: typically ordered annealed for machining, then heat treated)'
      section: limiting ruling section 30 mm
      heat_treatment: harden 815 to 845 C, oil or polymer quench; temper 455 to 650 C for at least 2 h, air cool (recommended ranges)
      tempering: 455 to 650 C recommended range; the datasheet gives one range for the whole process, not one tempering temperature per condition
      hardness_scale: HB
    method: Heat-treated mechanical properties table, value printed in this column; datasheet minimums and ranges kept as printed
    status: ground
    source: voestalpine-4340
    where: Mechanical Properties (heat treated) table, column Z*, row Hardness (HB)
    bound: lower
  - benchmark: density
    label: Density at 25 C (printed as x1000 kg/m3)
    value: 7.7
    value_high: 8.03
    bound: range
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 C
      unit_in_source: x1000 kg/m3
    method: eFunda Mechanical Properties table, range as printed; 1 g/cm3 equals 1000 kg/m3, so the printed numbers are kept and the unit is written as g/cm3
    status: ground
    source: efunda-4340
    where: Mechanical Properties table, Density row, 7.7 - 8.03 at 25 C
  - benchmark: poissons_ratio
    label: Poisson's ratio at 25 C
    value: 0.27
    value_high: 0.3
    bound: range
    unit: '-'
    scope: material
    conditions:
      temperature: 25 C
    method: eFunda Mechanical Properties table, range as printed
    status: ground
    source: efunda-4340
    where: Mechanical Properties table, Poisson's Ratio row, 0.27-0.30 at 25 C
  - benchmark: elastic_modulus
    label: Elastic modulus at 25 C
    value: 190
    value_high: 210
    bound: range
    unit: GPa
    scope: material
    conditions:
      temperature: 25 C
    method: eFunda Mechanical Properties table, range as printed
    status: ground
    source: efunda-4340
    where: Mechanical Properties table, Elastic Modulus row, 190 - 210 at 25 C
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, annealed at 810 C, 25 C
    value: 744.6
    unit: MPa
    scope: material
    conditions:
      temperature: 25 C
      treatment: annealed at 810 C (as printed by eFunda)
    method: eFunda Mechanical Properties table, single value on the row; the page offers more conditions behind a link, and those were not read
    status: ground
    source: efunda-4340
    where: Mechanical Properties table, Tensile Strength row, 744.6 MPa at 25 C, annealed at 810 C
  - benchmark: hardness_brinell
    label: Hardness, annealed at 810 C, 25 C
    value: 217
    unit: HB
    scope: material
    conditions:
      temperature: 25 C
      treatment: annealed at 810 C (as printed by eFunda)
      hardness_scale: HB
    method: eFunda Mechanical Properties table, single value on the row
    status: ground
    source: efunda-4340
    where: Mechanical Properties table, Hardness (HB) row, 217 at 25 C, annealed at 810 C
  - benchmark: impact_energy
    label: Izod impact energy, annealed at 810 C, 25 C
    value: 51.1
    unit: J
    scope: material
    conditions:
      test: Izod
      temperature: 25 C
      treatment: annealed at 810 C (as printed by eFunda)
    method: eFunda Mechanical Properties table, Impact Strength (Izod) row, single value
    status: ground
    source: efunda-4340
    where: Mechanical Properties table, Impact Strength (J) (Izod) row, 51.1 at 25 C, annealed at 810 C
  - benchmark: cte
    label: Coefficient of thermal expansion, 20 to 100 C, oil hardened and tempered 630 C
    value: 11.5
    unit: ppm/K
    scope: material
    conditions:
      temperature: 20 to 100 C
      treatment: oil hardened, tempered 630 C (as printed by eFunda)
      unit_in_source: 10^-6/degC
    method: eFunda Thermal Properties table, Thermal Expansion row; 10^-6 per degC is numerically the same as ppm/K
    status: ground
    source: efunda-4340
    where: Thermal Properties table, Thermal Expansion row, 11.5 at 20 to 100 C, oil hardened tempered 630 C
  - benchmark: hardness_rockwell_c
    label: Hardness, quenched and tempered bars (typical range)
    value: 24
    value_high: 38
    bound: range
    unit: HRC
    scope: material
    conditions:
      condition: quenched and tempered bars, typical range as the text states
      temper: not stated
      test: Rockwell or Brinell, as the text states
    method: 'Product page text: typical range stated for quenched and tempered bars (a sentence, not a table value)'
    status: ground
    source: saky-4340-flatbar
    where: Text under the heading 4340 Bar Hardness Test, sentence beginning For quenched and tempered bars
corrosion: []
risks:
  hazards:
    - text: 'PubChem aggregated GHS for elemental nickel (signal word Danger) from 4,778 company reports: H317 (99.9%), H372 (99.7%), H351 (72.9%), H412 (47.2%), H350 (22.5%), H360F (18%), H341 (13.5%) and H334 (10.3%) are the reported codes. 0.1% (5 of 4,778) of reports say it does not meet GHS criteria. The data cover the element, not this alloy.'
      ghs:
        - H317
        - H372
        - H351
        - H412
        - H350
        - H360F
        - H341
        - H334
      source: pubchem-nickel
      where: Safety and Hazards, GHS Classification, aggregated notifications (CID 935)
    - text: 'PubChem aggregated GHS for elemental chromium (signal word Danger) from 2,404 reports: H317 (20.7%), H334 (20.3%) and H319 (19.1%) are the reported codes. 50% (1,202 of 2,404) of reports say it does not meet GHS criteria. The data cover the element, not this alloy.'
      ghs:
        - H317
        - H334
        - H319
      source: pubchem-chromium
      where: Safety and Hazards, GHS Classification (CID 23976)
    - text: 'PubChem GHS for elemental molybdenum (signal word Danger) from 1,523 reports: H228 (30%), H361 (29.5%) and H225 (11.6%) are the reported codes. 57.4% (874 of 1,523) of reports say it does not meet GHS criteria. H225 (highly flammable liquid) does not fit a metal and is shown as printed. The data cover the element, not this alloy.'
      ghs:
        - H228
        - H361
        - H225
      source: pubchem-molybdenum
      where: Safety and Hazards, GHS Classification (CID 23932)
  failure_risks:
    - mode: Loss of toughness at the highest strength level
      trigger: Quenched and tempered to condition Z (limiting ruling section 30 mm), minimum yield strength 1125 MPa
      consequence: Minimum Charpy impact energy 9 J and minimum elongation 5 % (A5), with hardness above 444 HB, against minimum 42 J and 12 % at condition U (ruling section 100 mm). The datasheet gives minimums, not typical values.
      severity: moderate
      source: voestalpine-4340
      where: Mechanical Properties (heat treated) table, columns U and Z*
  side_effects: []
  handling:
    - text: 'Recommended heat treatment: normalise at 870 to 920 C for 10 to 20 minutes per 25 mm and air cool; anneal at 830 to 860 C and furnace cool; harden at 815 to 845 C for 10 to 20 minutes per 25 mm with an oil or polymer quench; temper at 455 to 650 C for at least 2 hours, then air cool.'
      source: voestalpine-4340
      where: Heat Treatment (recommended) rows
    - text: Stress relieve 30 to 50 C below the last tempering temperature after quench and temper; in the annealed condition stress relieve at 650 to 675 C.
      source: voestalpine-4340
      where: Stress Relieve rows
    - text: 'Supply condition: quenched and tempered to condition U and V, with surfaces black, peeled and polished, or rough machined. Asterisked conditions X, Y and Z are typically ordered annealed for machining and heat treated afterwards.'
      source: voestalpine-4340
      where: Supply condition table and footnote
    - text: 'Hardness check: for quenched and tempered bars the typical hardness is 24 to 38 HRC, measured by Rockwell or Brinell testing.'
      source: saky-4340-flatbar
      where: Text, 4340 Bar Hardness Test
  mitigations:
    - text: The datasheet says the addition of molybdenum prevents the steel from being susceptible to temper brittleness.
      source: voestalpine-4340
      where: Description
    - text: 'Use the lower strength conditions where toughness counts most: the minimum Charpy impact energy is 42 J at condition U and 9 J at condition Z.'
      source: voestalpine-4340
      where: Charpy Impact row, columns U and Z*
uses:
  - application: structures
    device: Aircraft landing gear assemblies, including struts and linkages
    example: Saky Steel lists aircraft landing gear assemblies, with struts and linkages, as an application of AISI 4340 flat bar.
    source: saky-4340-flatbar
    where: Applications list, item 1
  - application: mechanisms
    device: Gears, shafts and crankshafts
    example: Saky Steel lists automotive drivetrain gears and shafts, high-performance engine crankshafts, and heavy-duty gears and shafts for power transmission.
    source: saky-4340-flatbar
    where: Applications list, items 2, 4 and 5
  - application: mechanisms
    device: Forged hydraulic pistons, cylinders and fittings
    example: Saky Steel lists forged hydraulic system parts such as pistons, cylinders and fittings.
    source: saky-4340-flatbar
    where: Applications list, item 3
supply:
  - subject: Chromium
    abundance: World resources are greater than 12 billion tons of shipping-grade chromite, and 95 percent of world chromium resources are in Kazakhstan and southern Africa. US net import reliance was 79 percent of apparent consumption in 2025 (estimated).
    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
      - country: India
        share_percent: 5.9
        year: 2025
      - country: Brazil
        share_percent: 3.9
        year: 2025
      - country: Zimbabwe
        share_percent: 3.9
        year: 2025
    critical_lists:
      - list: USGS Final 2025 Critical Minerals List (MCS 2026 introduction, Table 6)
        listed: true
    recycling: Recycled chromium in reported stainless-steel scrap receipts was 21 percent of US apparent consumption in 2025.
    substitutes:
      - Chromium has no substitute in stainless steel, the leading end use, or in superalloys (USGS 2026).
    source: usgs-chromium-2026
    where: Salient Statistics; World Mine Production and Reserves, 2025e (shares calculated as printed tonnage over the 51,000 thousand t world total); World Resources; Substitutes; Recycling
  - subject: Molybdenum
    abundance: World reserves were 17,000 thousand t (USGS table). Identified resources are about 5.4 million tons in the United States and about 20 million tons in the rest of the world. Molybdenum is used principally as an alloying agent in cast iron, steel and superalloys. The Government of China imposed export controls on molybdenum powders in February 2025.
    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:
      - list: USGS Final 2025 Critical Minerals List (MCS 2026 introduction, Table 6)
        listed: false
    recycling: Molybdenum is recycled in catalysts, ferrous scrap and superalloy scrap; USGS says recycled molybdenum may be as much as 30 percent of apparent supply.
    substitutes:
      - 'USGS: there is little substitution for molybdenum in steels and cast irons; potential substitutes in alloy steels include boron, chromium, niobium (columbium) and vanadium.'
    source: usgs-molybdenum-2026
    where: Domestic Production and Use; World Mine Production and Reserves, 2025e (shares calculated over the 260,000 t world total); World Resources; Substitutes; Recycling
  - subject: Nickel
    abundance: Globally, nickel resources are estimated at more than 350 million tons, and the world reserve total is more than 140 million tons (USGS). In the United States, stainless and alloy steel and nickel-containing alloys typically account for more than 85 percent of domestic consumption.
    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
    critical_lists:
      - list: USGS Final 2025 Critical Minerals List (MCS 2026 introduction, Table 6)
        listed: true
    recycling: Nickel recovered from scrap accounted for about 60 percent of US apparent consumption in 2025 (estimated).
    substitutes:
      - 'USGS: low-nickel, duplex or ultrahigh-chromium stainless steels have been substituted for austenitic grades in construction; nickel-free specialty steels are sometimes used in place of stainless steel in power generation and petrochemical industries.'
    source: usgs-nickel-2026
    where: Salient Statistics; World Mine Production and Reserves, 2025e (shares calculated over the 3,900,000 t world total); World Resources; Substitutes; Recycling
media: []
documents:
  - title: 'voestalpine High Performance Metals: AISI 4340 / 1.6565 / G43400 datasheet (Australia)'
    type: datasheet
    url: https://www.voestalpine.com/highperformancemetals/australia/app/uploads/sites/265/2024/08/Datasheet-4340-2026-v1.pdf
  - title: 'eFunda: Properties of Alloy Steels, AISI 4340 (designations, composition, properties)'
    type: database
    url: https://www.efunda.com/materials/alloys/alloy_steels/show_alloy.cfm?id=aisi_4340&prop=all
  - title: 'Saky Steel: AISI 4340 Alloy Steel Flat Bar (stockist page)'
    type: datasheet
    url: https://www.sakysteel.com/aisi-4340-alloy-steel-flat-bar-high-strength-low-alloy-steel-supplier.html
  - title: 'Wikipedia: 4340 steel (equivalent-grade table and AMS reference list only)'
    type: database
    url: https://en.wikipedia.org/wiki/4340_steel
  - title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Molybdenum'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026, Introduction: Table 6, Final 2025 Critical Minerals List'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
    year: 2026
  - title: 'PubChem: Nickel (CID 935), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/935/JSON/?heading=GHS+Classification
    year: 2026
  - title: 'PubChem: Chromium (CID 23976), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23976/JSON/?heading=GHS+Classification
    year: 2026
  - title: 'PubChem: Molybdenum (CID 23932), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/JSON/?heading=GHS+Classification
    year: 2026
gaps:
  - No normalised mechanical properties were found. The voestalpine datasheet gives only the recommended normalising range (870 to 920 C), and no other source read in this run gives a normalised strength.
  - 'Annealed values come only from eFunda: tensile strength 744.6 MPa, hardness 217 HB and Izod impact 51.1 J at 25 C, annealed at 810 C. The voestalpine datasheet recommends annealing at 830 to 860 C, so both annealing temperatures are kept as printed.'
  - eFunda prints yield strength 472.3 MPa, elongation 22.0 % and reduction in area 49.9 % with no temperature or heat treatment, so these values are not recorded.
  - The quenched and tempered rows use the voestalpine ruling-section conditions and the recommended temper range 455 to 650 C. Only eFunda gives a specific temper (oil hardened, tempered 630 C), and that is recorded on its thermal expansion row only.
  - The Saky Steel product table prints tensile 850 to 1000 MPa, yield 680 to 860 MPa, elongation 14 % and hardness 24 to 28 HRC with no heat-treatment condition, so these values are not recorded.
  - The eFunda electrical resistivity row (248, unit printed as 10^-9 with a symbol-font character) is left out because the unit could not be confirmed from the text.
  - 'Corrosion: no corrosion test or service data for AISI 4340 were found in the sources read in this run. The 2021 ITATS paper covers AISI 1045, AISI 4140 and SS 304 only, and the datasheets give no corrosion statement, so the corrosion list is empty.'
  - Fracture toughness, fatigue, hydrogen embrittlement and notch values for AISI 4340 were not found in the sources read in this run. The Sandia hydrogen-compatibility reference (code 1211) has no AISI 4340 entry (checked in this run).
  - 'Launch-vehicle use: no source read in this run prints one for AISI 4340. The aerospace uses recorded are aircraft landing gear (Saky Steel) and the AMS specification numbers listed by eFunda.'
  - 'Designations left out: AMS 5331, AMS 6359 and AMS 6359B (listed by eFunda for AISI 4340), because no spec page was read to confirm their scope. AFNOR 35NCD6, JIS SNCM447, 35CrNiMo6, 40CrNiMo, 40KHN2MA and 36CrNiMo6 (in the Wikipedia equivalent-grade row) are also left out, because no standards page in this run confirms them.'
  - The Wikipedia AMS reference list names AMS6414M as Vacuum Consumable Electrode Remelted with UNS G43406. G43406 is a different UNS code and is not used here. The AMS 6414 and AMS 6415 spec documents were not read, so their product forms and melting practice are not confirmed.
  - The JIS designation SNCM 8 is printed by eFunda for AISI 4340, but no JIS standard page was read to confirm it.
  - 'Nearest-equivalent entries: DIN 1.6565, EN name 40NiCrMo6 and BS EN24 come from the voestalpine NEAREST STANDARDS table; 34CrNiMo6 and 1.6582 come from Saky Steel, which says the grade is commonly known as them. All five carry the note nearest equivalent.'
  - 'Composition: eFunda and Saky Steel print ranges (Saky Steel has no phosphorus or sulfur row). voestalpine prints single values under chemical analysis and does not label them as maxima. The recipe uses the eFunda ranges.'
  - Shares of world production are calculated from the USGS tonnage tables (2025e) over the printed world totals, because the USGS tables do not print shares.
  - 'Critical list: read from Table 6 of the Mineral Commodity Summaries 2026 introduction (PDF). Molybdenum is not in Table 6 and is recorded as not listed. The USGS web page for the list returned HTTP 403, and the EU critical raw materials list was not read.'
  - Hazards are PubChem records for the elements nickel, chromium and molybdenum, not for the alloy. No safety data sheet for AISI 4340 bar was read. PubChem molybdenum record lists H225 (highly flammable), which does not fit a metal; it is shown as printed. Welding and grinding fume hazards of the steel itself are not sourced.
  - The failure-risk severity rating is an assistant judgement, not a value from a source.
  - 'Benchmarks not in property-canon.yaml, used as snake_case names: impact_energy, hardness_brinell and hardness_rockwell_c.'
  - Density is printed in x1000 kg/m3 by eFunda; the value is written as g/cm3 with the printed unit kept in conditions.unit_in_source (1 g/cm3 equals 1000 kg/m3).
  - The Saky Steel page is a stockist page. Its applications list is the supplier statement, not a standard.
  - The Elgin 4340 fact sheet and the aircraftmaterials.com 4340 page could not be fetched in this run (not found), so they are not cited. No image was added to media.
sources:
  voestalpine-4340:
    title: 'voestalpine High Performance Metals: AISI 4340 / 1.6565 / G43400 datasheet'
    id: AISI 4340 / 1.6565 / G43400
    url: https://www.voestalpine.com/highperformancemetals/australia/app/uploads/sites/265/2024/08/Datasheet-4340-2026-v1.pdf
    kind: datasheet
    license: supplier datasheet, cited not reproduced
  efunda-4340:
    title: 'eFunda: Properties of Alloy Steels, AISI 4340'
    id: eFunda AISI 4340 page
    url: https://www.efunda.com/materials/alloys/alloy_steels/show_alloy.cfm?id=aisi_4340&prop=all
    kind: database
    license: eFunda website, cited not reproduced
  saky-4340-flatbar:
    title: 'Saky Steel: AISI 4340 Alloy Steel Flat Bar (stockist page)'
    id: AISI 4340 alloy steel flat bar
    url: https://www.sakysteel.com/aisi-4340-alloy-steel-flat-bar-high-strength-low-alloy-steel-supplier.html
    kind: datasheet
    license: supplier web page, cited not reproduced
  wiki-4340-steel:
    title: 'Wikipedia: 4340 steel'
    id: 4340 steel (equivalent-grade table and AMS reference list used)
    url: https://en.wikipedia.org/wiki/4340_steel
    kind: web
    license: CC BY-SA 4.0
  usgs-chromium-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    id: mcs2026-chromium
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-molybdenum-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Molybdenum'
    id: mcs2026-molybdenum
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-nickel-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    id: mcs2026-nickel
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-critical-2026:
    title: 'USGS Mineral Commodity Summaries 2026, Introduction: Table 6, Final 2025 Critical Minerals List'
    id: mcs2026 introduction, Table 6
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-nickel:
    title: 'PubChem: Nickel (CID 935), Safety and Hazards, GHS Classification'
    id: CID 935
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/935/JSON/?heading=GHS+Classification
    year: 2026
    kind: database
    license: PubChem terms (public)
  pubchem-chromium:
    title: 'PubChem: Chromium (CID 23976), Safety and Hazards, GHS Classification'
    id: CID 23976
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23976/JSON/?heading=GHS+Classification
    year: 2026
    kind: database
    license: PubChem terms (public)
  pubchem-molybdenum:
    title: 'PubChem: Molybdenum (CID 23932), Safety and Hazards, GHS Classification'
    id: CID 23932
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/JSON/?heading=GHS+Classification
    year: 2026
    kind: database
    license: PubChem terms (public)
license: CC-BY-4.0
updated: '2026-10-24'
review:
  status: draft
  method: assistant
  checked_values: 43
  unreachable: 5
  caveats: 4
  note: 'Read by an AI assistant on 2026-10-24 from pages fetched in this run: voestalpine AISI 4340 datasheet, eFunda AISI 4340, Saky Steel 4340 flat bar, Wikipedia 4340 steel, USGS MCS 2026 chromium, molybdenum, nickel and introduction, PubChem nickel, chromium and molybdenum. Unreachable: aircraftmaterials.com 4340 page (404), Elgin 4340 fact sheet (no such key), ASM Aerospace Specification Metals page (not found), steel-bar.com (138-byte response), USGS critical-list web page (403). Web search was unavailable in this run.'
story:
  recipe:
    line: AISI 4340 is an iron-based nickel-chromium-molybdenum steel. The composition ranges printed by eFunda are 0.38 to 0.43 percent carbon, 0.60 to 0.80 manganese, 0.15 to 0.30 silicon, 0.70 to 0.90 chromium, 1.65 to 2.00 nickel and 0.20 to 0.30 molybdenum, with phosphorus at 0.035 maximum, sulfur at 0.04 maximum and iron as the balance. Its strength comes from heat treatment (normalise, anneal, harden and temper) as much as from its composition.
    parts:
      - name: Iron
        symbol: Fe
        share_note: balance (the rest)
        role: The matrix of the steel. Heat treatment changes its structure from austenite to martensite and then tempered martensite.
        source: efunda-4340
        where: Composition table
      - name: Carbon
        symbol: C
        share_percent: 0.38
        share_high: 0.43
        role: Sets how hard the steel can become when quenched.
        source: efunda-4340
        where: Composition table, C row
      - name: Manganese
        symbol: Mn
        share_percent: 0.6
        share_high: 0.8
        role: Deoxidiser and hardenability aid in the melt.
        source: efunda-4340
        where: Composition table, Mn row
      - name: Silicon
        symbol: Si
        share_percent: 0.15
        share_high: 0.3
        role: Deoxidiser in the melt.
        source: efunda-4340
        where: Composition table, Si row
      - name: Chromium
        symbol: Cr
        share_percent: 0.7
        share_high: 0.9
        role: Adds hardenability and wear resistance. The grade is a low-alloy steel, not a stainless steel.
        source: efunda-4340
        where: Composition table, Cr row
      - name: Nickel
        symbol: Ni
        share_percent: 1.65
        share_high: 2
        role: Adds strength and toughness. voestalpine describes the grade as a nickel, chromium, molybdenum steel.
        source: efunda-4340
        where: Composition table, Ni row
      - name: Molybdenum
        symbol: Mo
        share_percent: 0.2
        share_high: 0.3
        role: Adds hardenability. The datasheet says it prevents temper brittleness.
        source: efunda-4340
        where: Composition table, Mo row
      - name: Phosphorus
        symbol: P
        share_percent: null
        share_high: 0.035
        share_note: maximum
        role: Impurity held low.
        source: efunda-4340
        where: Composition table, P row
      - name: Sulfur
        symbol: S
        share_percent: null
        share_high: 0.04
        share_note: maximum
        role: Impurity held low.
        source: efunda-4340
        where: Composition table, S row
  risk_groups:
    - title: For people
      level: 1
      verdict: Element records show sensitizer and cancer codes
      lead: No safety data sheet for AISI 4340 bar was read. The PubChem records below are for nickel, chromium and molybdenum as elements.
      points:
        - label: Nickel
          line: PubChem's aggregated record lists H317 (99.9%, allergic skin reaction), H351 (72.9%, suspected of causing cancer) and H372 (99.7%, organ damage from repeated exposure).
        - label: Chromium
          line: PubChem lists H317 (20.7%), H334 (20.3%) and H319 (19.1%). 50% (1,202 of 2,404) of reports say it does not meet GHS criteria.
        - label: Molybdenum
          line: PubChem lists H361 (29.5%, suspected of damaging fertility or the unborn child) and H228 (30%, flammable solid). 57.4% (874 of 1,523) of reports say it does not meet GHS criteria.
    - title: Heat treatment
      level: 1
      verdict: Toughness falls as strength rises
      lead: Strength comes from heat treatment, and the minimum toughness falls at the highest strength level.
      points:
        - label: Highest strength level
          line: At condition Z the minimum Charpy impact energy is 9 J and the minimum elongation is 5 percent, with hardness above 444 HB (voestalpine).
        - label: Tempering range
          line: The datasheet recommends tempering at 455 to 650 C for at least 2 hours and does not give one tempering temperature for each condition.
  why: AISI 4340 (UNS G43400) is a nickel-chromium-molybdenum steel for parts that must carry high tensile strength and toughness, particularly in large cross sections in the quenched and tempered condition (voestalpine). Its supplier says it has higher tensile and yield strength than 4140. Its strength depends on heat treatment, so every value in this profile carries its own condition.
  uses:
    - where: Aircraft landing gear
      line: Saky Steel says AISI 4340 flat bar is widely used for aircraft landing gear assemblies, including struts and linkages.
    - where: Gears, shafts and crankshafts
      line: The same supplier lists automotive drivetrain gears and shafts, high-performance engine crankshafts and heavy-duty gears and shafts for power transmission.
    - where: Forged hydraulic parts
      line: Forged hydraulic pistons, cylinders and fittings, which the supplier names as a use of the alloy.
  can_do:
    - label: Strength
      line: Quenched and tempered to condition U (100 mm ruling section), the minimum yield strength is 740 MPa and the tensile strength is 930 to 1080 MPa (voestalpine).
    - label: Toughness
      line: In the same condition the minimum Charpy impact energy is 42 J (voestalpine).
    - label: Annealed
      line: Annealed at 810 C and tested at 25 C, eFunda gives a tensile strength of 744.6 MPa and a hardness of 217 HB.
    - label: Stiffness and density
      line: At 25 C, eFunda gives an elastic modulus of 190 to 210 GPa and a density of 7.7 to 8.03 g/cm3 (printed as x1000 kg/m3).
    - label: Hardness
      line: For quenched and tempered bars the typical hardness is 24 to 38 HRC (Saky Steel).
  compare: The supplier describes AISI 4340 as a nickel, chromium and molybdenum steel with higher tensile and yield strength than 4140 (voestalpine). Its nickel content is 1.65 to 2.00 percent (eFunda). No 4140 values were read in this run, so this profile gives no numbers for the comparison.
  compare_rows:
    - label: Strength, quenched and tempered
      benchmark: yield_strength
    - label: Stiffness
      benchmark: elastic_modulus
    - label: Density
      benchmark: density
  handling:
    - Quote the heat-treatment condition with every strength value; the datasheet gives a separate row for each ruling-section condition.
    - Harden at 815 to 845 C with an oil or polymer quench, then temper at 455 to 650 C for at least 2 hours (recommended ranges).
    - Stress relieve 30 to 50 C below the last tempering temperature after quench and temper (voestalpine).
    - No safety data sheet for AISI 4340 bar was read in this run; take the supplier sheet for the bar you cut, grind or weld.
  good_for:
    - Large sections in the quenched and tempered condition that need high tensile strength and toughness (voestalpine).
    - Aircraft landing gear struts and linkages, and gears and shafts, which the stockist lists as main uses (Saky Steel).
  watch_out:
    - 'Toughness falls as strength rises: the minimum Charpy impact energy is 42 J at condition U (yield 740 MPa) and 9 J at condition Z (yield 1125 MPa).'
    - The tempering temperature for each condition is not printed; the recommended range is 455 to 650 C.
    - 'The annealing temperature differs between sources: eFunda gives 810 C and voestalpine gives 830 to 860 C.'
    - No corrosion data for AISI 4340 were read in this run.
  verdict: AISI 4340 is a strong, tough nickel-chromium-molybdenum steel for large heat-treated sections, and its supplier names aircraft landing gear among its uses. Its values change with the ruling section and the temper, so quote the condition with each one. The figures are supplier minimums, and no corrosion or hydrogen data were read in this run.