300M ultra-high-strength steel (UNS K44220) 300M (UNS K44220)

spore: profile
id: steel-300m
spore_version: '0.2'
family: carbon-and-alloy-steels
name: 300M ultra-high-strength steel (UNS K44220)
abbreviation: 300M (UNS K44220)
role: structural alloy
category: metals
type: steels-and-stainless
summary: 300M is a vacuum-melted alloy steel of the 4340 family, modified with more silicon and vanadium, and sold to AMS 6417 for aircraft landing gear and high-load fittings. Its UNS number is K44220. Service Steel Aerospace gives a minimum longitudinal tensile strength of 270 ksi and a minimum yield strength of 220 ksi for AMS 6417. NeoNickel gives a hardness of 53 HRC after tempering at 204 °C, falling to 35 HRC at 649 °C. The supplier pages read for this profile give no corrosion data for this grade.
best_for: Through-hardened landing gear and high-load fittings that need a minimum tensile strength of 270 ksi (AMS 6417, per Service Steel Aerospace).
weakest_at: 'Heavy sections and hot tempering: hardness falls as tempering temperature rises, and minimum reduction of area drops to 15 % over 225 in2 (AMS 6417 table). No corrosion data were found.'
identity:
  formula: Fe balance; C 0.38 to 0.43 (SSA table; 0.37 to 0.43 in its introduction; NeoNickel 0.38 to 0.46 as max), Mn 0.65 to 0.90, Si 1.45 to 1.80, Cr 0.70 to 0.95, Ni 1.65 to 2.00, Mo 0.30 to 0.50 (NeoNickel 0.3 to 0.65), V 0.05 to 0.10, max 0.010 P, max 0.008 S, max 0.35 Cu (percent, as printed on the SSA Chemical Composition table). Titanium Industries prints the same SSA ranges for C, Mn, Si, Cr, Ni, Mo and V.
  source: ssa-300m
  where: Chemical Composition table (SSA). Titanium Industries Table 1 and NeoNickel Chemical analysis table give the same elements with minor differences.
  designations:
    - system: UNS
      code: K44220
      source: ssa-300m
      where: Page title and Common Specifications, UNS K44220
    - system: AMS
      code: '6417'
      source: ssa-300m
      where: Common Specifications, AMS 6417 (Replaces MIL-S-83135)
    - system: AMS
      code: '6257'
      source: ssa-300m
      where: Common Specifications, AMS 6257 (Replaces MIL-S-8844 REV D CLASS 3)
    - system: AMS
      code: '6419'
      source: ssa-300m
      where: Common Specifications, AMS 6419
    - system: SAE
      code: 434M
      source: ssa-300m
      where: Common Specifications, SAE 434M
    - system: ASTM
      code: A646
      source: ssa-300m
      where: Common Specifications, ASTM A646
    - system: AISI
      code: 300M
      source: titanium-300m
      where: Page title, AISI 300M (4340 MOD)
    - system: Trade name
      code: Lescalloy 300M Vac-Arc
      source: ssa-300m
      where: Common Trade Names
    - system: Trade name
      code: 300M CEVM
      source: ssa-300m
      where: Common Trade Names
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - mechanisms
properties:
  - benchmark: density
    label: Density, 300M/S155 (NeoNickel)
    value: 7.85
    unit: g/cm3
    scope: material
    conditions:
      condition: not stated on the page
      alloy: 300M/S155 as named by NeoNickel
      unit_in_source: g/cm^3
    method: Value printed in the Key Properties list of a supplier product page
    status: ground
    source: neonickel-300m
    where: Key Properties list, Density
  - benchmark: density
    label: Density, AMS 6417 300M (SSA)
    value: 0.2836
    unit: lb/in3
    scope: material
    conditions:
      condition: not stated on the page
      alloy: 300M (4340 MOD), AMS 6417
      unit_in_source: '#/in 3'
    method: Value printed in the Physical Properties block of a supplier product page
    status: ground
    source: ssa-300m
    where: Physical Properties block, Density
  - benchmark: melting_point
    label: Melting point, UNS K44220
    value: 2590
    unit: °F
    scope: material
    conditions:
      alloy: Alloy Steel 4340 MOD 300M, UNS K44220
      pressure: not stated
      basis: single value printed; no solidus or liquidus split
      unit_in_source: °F
    method: Single value printed in the physical properties block of a supplier data table
    status: ground
    source: titanium-300m
    where: Table 2, PHYSICAL PROPERTIES, row Melting Point (°F)
  - benchmark: specific_heat
    label: Specific heat capacity, 300M/S155 (NeoNickel)
    value: 448
    unit: J/kg*K
    scope: material
    conditions:
      temperature: not stated on the page
      alloy: 300M/S155 as named by NeoNickel
      unit_in_source: J/kg*K
    method: Value printed in the Key Properties list of a supplier product page
    status: ground
    source: neonickel-300m
    where: Key Properties list, Specific Heat Capacity
  - benchmark: cte
    label: Coefficient of thermal expansion, 300M/S155 (NeoNickel)
    value: 11.34
    unit: µm/mm/°C
    scope: material
    conditions:
      temperature_range: '-17.8 °C to 93 °C (printed as -17.8-93°C)'
      alloy: 300M/S155 as named by NeoNickel
      unit_in_source: µm/mm/°C
    method: Value printed in the Key Properties list of a supplier product page
    status: ground
    source: neonickel-300m
    where: Key Properties list, Coefficient of Thermal Expansion
  - benchmark: hardness_rockwell_c
    label: Hardness after tempering at 204 °C
    value: 53
    unit: HRC
    scope: material
    conditions:
      tempering_temperature: 204 °C
      austenitising: 871 °C for 1 hour, oil quench
      tempering_time: 2 + 2 hour, air cool
      hardness_scale: Rockwell C
      unit_in_source: Rockwell C
    method: Value in the hardness versus tempering temperature table of a supplier product page
    status: ground
    source: neonickel-300m
    where: Hardness at Various Tempering Temperature table, column 204°C, row Hardness / Rockwell C
  - benchmark: hardness_rockwell_c
    label: Hardness after tempering at 316 °C
    value: 52.5
    unit: HRC
    scope: material
    conditions:
      tempering_temperature: 316 °C
      austenitising: 871 °C for 1 hour, oil quench
      tempering_time: 2 + 2 hour, air cool
      hardness_scale: Rockwell C
      unit_in_source: Rockwell C
    method: Value in the hardness versus tempering temperature table of a supplier product page
    status: ground
    source: neonickel-300m
    where: Hardness at Various Tempering Temperature table, column 316°C, row Hardness / Rockwell C
  - benchmark: hardness_rockwell_c
    label: Hardness after tempering at 427 °C
    value: 50
    unit: HRC
    scope: material
    conditions:
      tempering_temperature: 427 °C
      austenitising: 871 °C for 1 hour, oil quench
      tempering_time: 2 + 2 hour, air cool
      hardness_scale: Rockwell C
      unit_in_source: Rockwell C
    method: Value in the hardness versus tempering temperature table of a supplier product page
    status: ground
    source: neonickel-300m
    where: Hardness at Various Tempering Temperature table, column 427°C, row Hardness / Rockwell C
  - benchmark: hardness_rockwell_c
    label: Hardness after tempering at 538 °C
    value: 47
    unit: HRC
    scope: material
    conditions:
      tempering_temperature: 538 °C
      austenitising: 871 °C for 1 hour, oil quench
      tempering_time: 2 + 2 hour, air cool
      hardness_scale: Rockwell C
      unit_in_source: Rockwell C
    method: Value in the hardness versus tempering temperature table of a supplier product page
    status: ground
    source: neonickel-300m
    where: Hardness at Various Tempering Temperature table, column 538°C, row Hardness / Rockwell C
  - benchmark: hardness_rockwell_c
    label: Hardness after tempering at 649 °C
    value: 35
    unit: HRC
    scope: material
    conditions:
      tempering_temperature: 649 °C
      austenitising: 871 °C for 1 hour, oil quench
      tempering_time: 2 + 2 hour, air cool
      hardness_scale: Rockwell C
      unit_in_source: Rockwell C
    method: Value in the hardness versus tempering temperature table of a supplier product page
    status: ground
    source: neonickel-300m
    where: Hardness at Various Tempering Temperature table, column 649°C, row Hardness / Rockwell C
  - benchmark: yield_strength
    label: Yield strength 0.2% offset, longitudinal minimum (AMS 6417)
    value: 220
    bound: lower
    unit: ksi
    scope: material
    conditions:
      specification: AMS 6417, minimum longitudinal, after heat treating per paragraph 3.4.4 (as cited by SSA)
      strength_type: 0.2% offset
      heat_treatment: normalise 927 °C, harden 871 °C in oil, temper 204 to 649 °C (SSA heat treatment table)
      unit_in_source: ksi
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 longitudinal requirement
    status: ground
    source: ssa-300m
    where: Minimum Longitudinal Tensile Properties per AMS 6417 table, row Yield Strength 0.2% offset
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, longitudinal minimum (AMS 6417)
    value: 270
    bound: lower
    unit: ksi
    scope: material
    conditions:
      specification: AMS 6417, minimum longitudinal, after heat treating per paragraph 3.4.4 (as cited by SSA)
      heat_treatment: normalise 927 °C, harden 871 °C in oil, temper 204 to 649 °C (SSA heat treatment table)
      unit_in_source: ksi
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 longitudinal requirement
    status: ground
    source: ssa-300m
    where: Minimum Longitudinal Tensile Properties per AMS 6417 table, row Tensile Strength
  - benchmark: elongation
    label: Elongation, longitudinal minimum (AMS 6417)
    value: 8
    bound: lower
    unit: '%'
    scope: material
    conditions:
      specification: AMS 6417, minimum longitudinal (as cited by SSA)
      gauge: not stated on the page
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 longitudinal requirement
    status: ground
    source: ssa-300m
    where: Minimum Longitudinal Tensile Properties per AMS 6417 table, row Elongation
  - benchmark: reduction_of_area
    label: Reduction of area, longitudinal minimum (AMS 6417)
    value: 30
    bound: lower
    unit: '%'
    scope: material
    conditions:
      specification: AMS 6417, minimum longitudinal (as cited by SSA)
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 longitudinal requirement
    status: ground
    source: ssa-300m
    where: Minimum Longitudinal Tensile Properties per AMS 6417 table, row Reduction of Area
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, transverse minimum, cross-section up to 100 in2
    value: 270
    bound: lower
    unit: ksi
    scope: material
    conditions:
      orientation: transverse
      cross_section: up to 100 in2, incl (AMS 6417, as cited by SSA)
      unit_in_source: ksi
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 transverse requirement
    status: ground
    source: ssa-300m
    where: Minimum Transverse Tensile Properties per AMS 6417 table, row Up to 100 in2, incl, column Tensile Strength
  - benchmark: yield_strength
    label: Yield strength 0.2% offset, transverse minimum, cross-section up to 100 in2
    value: 220
    bound: lower
    unit: ksi
    scope: material
    conditions:
      orientation: transverse
      cross_section: up to 100 in2, incl (AMS 6417, as cited by SSA)
      strength_type: 0.2% offset
      unit_in_source: ksi
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 transverse requirement
    status: ground
    source: ssa-300m
    where: Minimum Transverse Tensile Properties per AMS 6417 table, row Up to 100 in2, incl, column Yield Strength 0.2% Offset
  - benchmark: reduction_of_area
    label: Reduction of area, transverse average minimum, cross-section up to 100 in2
    value: 30
    bound: lower
    unit: '%'
    scope: material
    conditions:
      orientation: transverse
      cross_section: up to 100 in2, incl
      measure: average reduction of area (individual minimum 25 %)
      specification: AMS 6417 (as cited by SSA)
    method: Minimum value printed in a supplier table that reproduces the AMS 6417 transverse requirement
    status: ground
    source: ssa-300m
    where: Minimum Transverse Tensile Properties per AMS 6417 table, row Up to 100 in2, incl, column Avg. Reduction of Area
corrosion: []
risks:
  hazards:
    - text: PubChem's GHS record for nickel metal (CID 935) lists H317, H351 and H372, with signal word Danger and pictograms GHS07 and GHS08. Nickel is 1.65 to 2.00 % of 300M by the SSA chemistry table, so these hazards describe a constituent, not the finished steel. No safety data sheet for 300M itself was read in this run.
      ghs:
        - H317
        - H351
        - H372
      source: pubchem-nickel
      where: GHS Classification section, Signal, GHS Hazard Statements and Pictogram(s) rows (PubChem CID 935 record)
  failure_risks:
    - mode: Softening on hot tempering
      trigger: Tempering toward the hot end of the 204 °C to 649 °C range
      consequence: 'Hardness falls at each step up in tempering temperature: 53 HRC at 204 °C, 52.5 HRC at 316 °C, 50 HRC at 427 °C, 47 HRC at 538 °C and 35 HRC at 649 °C. The NeoNickel table gives hardness only, not strength at each temperature.'
      severity: moderate
      source: neonickel-300m
      where: Hardness at Various Tempering Temperature table, row Hardness / Rockwell C
    - mode: Lower reduction of area in heavy sections
      trigger: Cross-section over 100 in2, and most of all over 225 in2
      consequence: The AMS 6417 minimum transverse reduction of area falls from 30 % (up to 100 in2) to 15 % (over 225 in2), with an individual minimum of 10 %. The tensile and yield minima stay at 270 ksi and 220 ksi in the table.
      severity: moderate
      source: ssa-300m
      where: Minimum Transverse Tensile Properties (AMS 6417) table, rows Up to 100 in2, incl and Over 225 in2
    - mode: Section size limit on through-hardening
      trigger: Sections thicker than 3.5 in in cross-section
      consequence: SSA describes the grade for through-hardness in sections 3.5 in and under, which need a minimum of 52 HRC. The page gives no property data for thicker sections.
      severity: moderate
      source: ssa-300m
      where: Applications paragraph
  side_effects: []
  handling:
    - text: 'Heat treat to the supplier cycle: normalise at 927 °C +/- 14 °C and air cool, harden at 871 °C +/- 14 °C in oil, then temper between 204 °C and 649 °C (double temper, depending on the strength and hardness wanted).'
      source: ssa-300m
      where: AMS 6417 Heat Treatment table
    - text: Forge between 1066 °C and 1232 °C, with a minimum forging temperature of 1700 °F.
      source: ssa-300m
      where: AMS 6417 Fabrication table, Forging row
    - text: Machine after normalising and tempering at about 649 °C (1200 °F), the condition SSA gives for the best machinability.
      source: ssa-300m
      where: AMS 6417 Fabrication table, Machinability row
    - text: Titanium Industries says its alloy data are for reference only and not for design.
      source: titanium-300m
      where: Product description, disclaimer
  mitigations: []
uses:
  - application: structures
    device: Aircraft landing gear
    example: SSA lists aircraft landing gear first among its applications and says 300M is widely used for it. Titanium Industries also lists aircraft landing gear as a typical use.
    source: ssa-300m
    where: Applications list; Titanium Industries typical uses paragraph
  - application: structures
    device: Airframe parts, such as flap tracks
    example: SSA lists airframe parts such as flap tracks, and Titanium Industries lists airframe parts and flap track among typical uses.
    source: ssa-300m
    where: Applications list
  - application: mechanisms
    device: Gears, shafts and high-strength bolts
    example: NeoNickel lists undercarriage components, gears and shafts, and high strength bolts among its applications for 300M/S155.
    source: neonickel-300m
    where: About 300M/S155 paragraph and Applications list
supply:
  - subject: Iron and steel (raw steel, the base of 300M)
    abundance: World raw steel production in 2025e was 1,900 million metric tons (USGS). China produced 980 million metric tons, India 160 million and the United States 82 million.
    producers:
      - country: China
        share_percent: 51.6
        year: 2025
      - country: India
        share_percent: 8.4
        year: 2025
      - country: United States
        share_percent: 4.3
        year: 2025
    critical_lists: []
    recycling: Not read in the USGS iron and steel summary for this run.
    substitutes:
      - 'USGS: iron and steel compete either with less expensive nonmetallic materials or with more expensive materials that have a performance advantage.'
    source: usgs-iron-steel-2026
    where: World Production table, Raw steel 2025e column (shares calculated by Space Mushroom from the printed country and world values)
  - subject: Nickel (1.65 to 2.00 % of 300M)
    abundance: World nickel mine production was 3,900,000 metric tons in 2025e (USGS), with Indonesia at 2,600,000 metric tons.
    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
    critical_lists: []
    substitutes: []
    source: usgs-nickel-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated by Space Mushroom from the printed values)
  - subject: Chromium (0.70 to 0.95 % of 300M)
    abundance: World chromite mine production was 51,000 thousand metric tons in 2025e (gross weight, per the USGS table note). South Africa produced 23,000 thousand metric tons.
    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: []
    substitutes: []
    source: usgs-chromium-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated by Space Mushroom from the printed values)
  - subject: Molybdenum (0.30 to 0.50 % of 300M)
    abundance: World molybdenum mine production was 260,000 metric tons of molybdenum content in 2025e (USGS). China produced 97,000 and Chile 42,000 metric tons.
    producers:
      - country: China
        share_percent: 37.3
        year: 2025
      - country: Chile
        share_percent: 16.2
        year: 2025
      - country: Peru
        share_percent: 15
        year: 2025
    critical_lists: []
    substitutes: []
    source: usgs-molybdenum-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated by Space Mushroom from the printed values)
  - subject: Vanadium (0.05 to 0.10 % of 300M)
    abundance: World vanadium mine production was 110,000 metric tons of vanadium content in 2025e (USGS). China produced 82,000 and Russia 21,000 metric tons.
    producers:
      - country: China
        share_percent: 74.5
        year: 2025
      - country: Russia
        share_percent: 19.1
        year: 2025
      - country: Brazil
        share_percent: 4.8
        year: 2025
    critical_lists: []
    substitutes: []
    source: usgs-vanadium-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated by Space Mushroom from the printed values)
documents:
  - title: 'Service Steel Aerospace: 300M (4340 MOD) Alloy Steel, AMS 6417, UNS K44220'
    type: datasheet
    url: https://ssa-corp.com/es/300M-4340-MOD_AMS-6417-UNSK44220.php
  - title: 'Titanium Industries: Alloy Steel 4340 MOD 300M (UNS K44220)'
    type: datasheet
    url: https://titanium.com/alloys/alloy-steels/alloy-steel-aisi-4340-mod-300m/
  - title: 'NeoNickel: 300M/S155 High Performance Alloy Steel'
    type: datasheet
    url: https://www.neonickel.com/alloys/all-alloys/300ms155
  - title: 'USGS Mineral Commodity Summaries 2026: Iron and Steel'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-steel.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: 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: Vanadium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-vanadium.pdf
    year: 2026
  - title: PubChem compound record for nickel, CID 935 (GHS classification, PUG View JSON)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/935/JSON
gaps:
  - Corrosion, stress corrosion and hydrogen embrittlement data for 300M were not found. The web search budget for this run ran out before those queries could run, and no corrosion source was read. The corrosion list is empty for this reason.
  - No safety data sheet for 300M itself was read. The hazard entry uses the PubChem GHS record for nickel, a 1.65 to 2.00 % constituent, and says so.
  - No EN, DIN or JIS designation is printed on any of the three supplier pages read, so none is listed. NeoNickel prints ASTM A579 for this grade; it is not recorded because it is not printed with the other designations on a source page checked here.
  - Elastic modulus, fracture toughness, fatigue strength, Charpy impact energy, and the mechanical properties at each tempering temperature (not hardness alone) were not in the pages read.
  - The NeoNickel page prints an 'Ultimate Tensile Strength /MPa' row with values 1981, 1672, 35, 10 and 58 at 21 °C. The column labels are not clear on the page, so none of these values is recorded.
  - The melting point is given only as 2590 °F, with no solidus or liquidus split and no pressure.
  - Density and composition ranges differ slightly between suppliers. Both values are recorded (NeoNickel carbon max 0.46 and molybdenum 0.3 to 0.65; SSA carbon 0.38 to 0.43 and molybdenum 0.30 to 0.50). The SSA introduction gives carbon as 0.37 to 0.43, which is also recorded.
  - Reduction of area and hardness are not canonical benchmark names in the property list (reduction_of_area and hardness_rockwell_c were used). Both are short snake_case names as the brief allows.
  - Strengths are kept in ksi as the source prints them; they are not converted to MPa on this page.
  - The USGS critical minerals lists were not read in the iron and steel, nickel, chromium, molybdenum or vanadium summaries, so critical_lists is empty.
  - Some countries in the USGS chromium, molybdenum and vanadium tables are marked 'e' with values not shown on the same row, so the shares cover only the printed countries and the printed world total.
  - No radiation, outgassing, atomic oxygen or space-environment data for 300M were found in the sources read.
sources:
  ssa-300m:
    title: 300M (4340 MOD) Alloy Steel - AMS 6417 - UNS K44220, Service Steel Aerospace Corp. product page
    id: UNS K44220; AMS 6417; AMS 6257; AMS 6419; SAE 434M; ASTM A646
    url: https://ssa-corp.com/es/300M-4340-MOD_AMS-6417-UNSK44220.php
    kind: datasheet
    license: Supplier product page (cited, not reproduced)
  titanium-300m:
    title: Alloy Steel 4340 MOD 300M (UNS K44220), Titanium Industries product page
    id: UNS K44220; AISI 300M (4340 MOD); AMS 2300, AMS 6257, AMS 6417, AMS 6419; SAE 434M; ASTM A646
    url: https://titanium.com/alloys/alloy-steels/alloy-steel-aisi-4340-mod-300m/
    kind: datasheet
    license: Supplier product page (cited, not reproduced)
  neonickel-300m:
    title: 300M/S155 High Performance Alloy Steel, NeoNickel product page
    id: UNS K44220; ASTM A579; AMS 6417
    url: https://www.neonickel.com/alloys/all-alloys/300ms155
    kind: datasheet
    license: Supplier product page (cited, not reproduced)
  usgs-iron-steel-2026:
    title: 'Mineral Commodity Summaries 2026: Iron and Steel (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iron-steel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-nickel-2026:
    title: 'Mineral Commodity Summaries 2026: Nickel (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-chromium-2026:
    title: 'Mineral Commodity Summaries 2026: Chromium (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-molybdenum-2026:
    title: 'Mineral Commodity Summaries 2026: Molybdenum (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-vanadium-2026:
    title: 'Mineral Commodity Summaries 2026: Vanadium (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-vanadium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-nickel:
    title: 'PubChem compound record: Nickel, CID 935 (GHS classification)'
    id: CID 935
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/935/JSON
    kind: database
    license: PubChem (NCBI), public domain; GHS data attributed to contributing sources
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 17
  unreachable: 0
  caveats: 4
  note: 'Values read by an AI assistant on 2026-11-01 from the supplier pages and USGS PDFs named in each entry. Caveats: supplier strengths are AMS 6417 minimums reproduced by a distributor, not the AMS document; the NeoNickel tensile row is unclear and was not used; hardness at tempering is from one supplier table; supply shares are calculated from printed values.'
story:
  risk_groups:
    - title: For people
      lead: The hazard statements found are for nickel, a constituent of 300M, not for the finished steel. No safety data sheet for 300M was read.
      level: 2
      verdict: Nickel hazards only, from PubChem
      points:
        - label: Nickel in the steel
          line: PubChem's GHS record for nickel metal lists H317, H351 and H372, with signal word Danger. Nickel is 1.65 to 2.00 % of 300M, so these describe a constituent.
    - title: If it fails
      lead: The failure routes in the sources are over-tempering and heavy sections. These are supplier data, not test results on failed parts.
      level: 2
      verdict: Hardness and area limits
      points:
        - label: Hot tempering
          line: Hardness falls from 53 HRC at 204 °C tempering to 35 HRC at 649 °C tempering (NeoNickel table).
        - label: Heavy sections
          line: Minimum reduction of area falls from 30 % up to 100 in2 to 15 % over 225 in2 (SSA table). Through-hardening is described only for sections 3.5 in and under.
    - title: Handling and storage
      points:
        - label: Heat treatment
          line: Normalise at 927 °C, harden at 871 °C in oil, then temper between 204 °C and 649 °C (SSA).
        - label: Forging and machining
          line: Forge between 1066 °C and 1232 °C, with a minimum of 1700 °F. Machine after tempering at about 649 °C.
  why: '300M is a vacuum-melted alloy steel of the 4340 family, and Service Steel Aerospace describes it as 4340 steel with added vanadium and higher silicon. Its AMS 6417 longitudinal minimums are 220 ksi yield strength and 270 ksi tensile strength, with 8 % elongation and 30 % reduction of area. Its hardness depends on the tempering temperature: 53 HRC after tempering at 204 °C and 35 HRC at 649 °C. Landing gear uses it because the suppliers list high strength, good toughness, fatigue strength and ductility together.'
  uses:
    - where: Landing gear
      line: Aircraft landing gear is the first application that Service Steel Aerospace lists for 300M, and Titanium Industries lists it too.
    - where: Airframe parts
      line: Both SSA and Titanium Industries list airframe parts, including flap tracks, and missile components and motorsport parts appear on the SSA list.
    - where: Gears and bolts
      line: NeoNickel lists undercarriage components, gears, shafts and high strength bolts for its 300M/S155.
  can_do:
    - label: Carry the load
      value: 270 ksi minimum
      benchmark: ultimate_tensile_strength
      line: The AMS 6417 longitudinal minimum tensile strength is 270 ksi and the minimum yield strength is 220 ksi, per SSA.
    - label: Stay hard through the section
      value: 52 HRC minimum
      benchmark: hardness_rockwell_c
      line: SSA says the grade is used for through-hardness in sections 3.5 in and under, with a minimum of 52 HRC.
    - label: Weight
      value: 7.85 g/cm3
      benchmark: density
      line: Density is 7.85 g/cm3 on the NeoNickel page and 0.2836 lb/in3 on the SSA page.
    - label: Melting
      value: 2590 °F
      benchmark: melting_point
      line: The Titanium Industries table gives a melting point of 2590 °F for UNS K44220.
  compare: Service Steel Aerospace describes 300M as 4340 alloy steel modified with added vanadium and higher silicon, and the chemistry ranges show it with a higher molybdenum range. The two grades have different specifications, so read the table rows as examples of what each grade gives, not as a ranking.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Yield strength
      benchmark: yield_strength
    - label: Hardness after tempering
      benchmark: hardness_rockwell_c
  handling:
    - 'Specify the tempering temperature: hardness falls from 53 HRC at 204 °C to 35 HRC at 649 °C (NeoNickel).'
    - Forge between 1066 °C and 1232 °C and keep the minimum forging temperature at 1700 °F (SSA).
    - Treat the supplier data as reference values, since Titanium Industries says its alloy data are not for design.
  good_for:
    - Landing gear and high-load fittings that need a 270 ksi minimum tensile strength (SSA, AMS 6417).
    - Gears, shafts and high-strength bolts (NeoNickel lists these).
  watch_out:
    - Hardness falls as tempering temperature rises, from 53 HRC at 204 °C to 35 HRC at 649 °C (NeoNickel).
    - 'Heavy sections: minimum reduction of area falls to 15 % over 225 in2 (SSA).'
    - No corrosion or hydrogen-embrittlement data for 300M were found in this run.
  verdict: 300M gives AMS 6417 longitudinal minimums of 270 ksi tensile and 220 ksi yield strength, with hardness set by the tempering temperature. It is a 4340-type alloy steel with added vanadium and higher silicon. The supplier pages used give no corrosion data, and the alloying metals come from few producing countries, as the USGS tables show.
  recipe:
    line: 300M is an iron-based alloy steel of the 4340 family, made by vacuum melting (SSA names the process consumable electrode vacuum remelting, CEVM). The parts below are the SSA chemistry ranges in percent. NeoNickel prints carbon up to 0.46 and molybdenum from 0.3 to 0.65, so the two sources differ on those elements.
    parts:
      - name: Iron
        symbol: Fe
        role: Matrix of the steel
        share_note: balance
        source: ssa-300m
        where: Chemical Composition table; NeoNickel prints Fe as Balance
      - name: Carbon
        symbol: C
        role: Strength and hardness after heat treatment
        share_percent: 0.38
        share_high: 0.43
        source: ssa-300m
        where: Chemical Composition table, row C
      - name: Manganese
        symbol: Mn
        role: Alloying element; the pages do not say what it does
        share_percent: 0.65
        share_high: 0.9
        source: ssa-300m
        where: Chemical Composition table, row Mn
      - name: Silicon
        symbol: Si
        role: 'Raised above 4340 (SSA: higher silicon)'
        share_percent: 1.45
        share_high: 1.8
        source: ssa-300m
        where: Chemical Composition table, row Si
      - name: Chromium
        symbol: Cr
        role: Alloying element; the pages do not say what it does
        share_percent: 0.7
        share_high: 0.95
        source: ssa-300m
        where: Chemical Composition table, row Cr
      - name: Nickel
        symbol: Ni
        role: Alloying element, as in 4340
        share_percent: 1.65
        share_high: 2
        source: ssa-300m
        where: Chemical Composition table, row Ni
      - name: Molybdenum
        symbol: Mo
        role: 'Raised above 4340 (Titanium Industries: high molybdenum content)'
        share_percent: 0.3
        share_high: 0.5
        source: ssa-300m
        where: Chemical Composition table, row Mo
      - name: Vanadium
        symbol: V
        role: Added to the 4340 base (SSA)
        share_percent: 0.05
        share_high: 0.1
        source: ssa-300m
        where: Chemical Composition table, row V
      - name: Phosphorus
        symbol: P
        role: Impurity limit
        share_note: max 0.010 %
        source: ssa-300m
        where: Chemical Composition table, row P
      - name: Sulfur
        symbol: S
        role: Impurity limit
        share_note: max 0.008 %
        source: ssa-300m
        where: Chemical Composition table, row S
      - name: Copper
        symbol: Cu
        role: Residual element limit
        share_note: max 0.35 %
        source: ssa-300m
        where: Chemical Composition table, row Cu