spore: profile
id: steel-4130
spore_version: '0.2'
family: carbon-and-alloy-steels
name: Alloy steel AISI 4130 (chromium-molybdenum)
abbreviation: 4130 (UNS G41300)
role: structural alloy
category: metals
type: steels-and-stainless
summary: AISI 4130 is a low-alloy chromium-molybdenum steel (UNS G41300) that is widely used for aircraft tube, sheet and bar and for oil and gas parts. Its strength depends on heat treatment, so each value in this file carries its own condition. Hydrogen gas and salt solutions reduce its crack and fatigue resistance in laboratory tests.
best_for: Aircraft and motorsport tube, sheet and bar, and oil and gas parts, where weldability and strength after heat treatment both matter
weakest_at: 'Hydrogen gas and salt solutions: in one laboratory study the threshold stress intensity fell from 88 to 32 MPa√m as hydrogen pressure rose from 21 to 69 MPa, and salt solution cut corrosion-fatigue life'
identity:
  formula: Fe balance; 0.28 to 0.33 C, 0.40 to 0.60 Mn, 0.15 to 0.35 Si, 0.80 to 1.10 Cr, 0.15 to 0.25 Mo, 0.035 max P, 0.040 max S (wt%, allowable ranges printed in Table 1.1.1 of the Sandia reference)
  source: sandia-1211
  where: Table 1.1.1, Allowable composition ranges (wt%) for Cr-Mo steels, row 4130 (UNS G41300)
  designations:
    - system: UNS
      code: G41300
      source: aircraft-4130
      where: Specifications list, UNS G41300
    - system: AISI
      code: '4130'
      source: aircraft-4130
      where: Specifications list, AISI 4130; page title
    - system: SAE
      code: '4130'
      source: titanium-4130
      where: 'Introduction: also known as AISI or SAE 4130'
    - system: SAE
      code: J404
      source: sandia-1211
      where: 'Section 1.2, common names: SAE J404 (4130)'
    - system: ASTM
      code: A29
      note: grade 4130 (as printed)
      source: sandia-1211
      where: 'Section 1.2, common names: ASTM A29 (4130)'
    - system: ASTM
      code: A322
      source: aircraft-4130
      where: Specifications list, ASTM A322
    - system: ASTM
      code: A331
      source: aircraft-4130
      where: Specifications list, ASTM A331
    - system: ASTM
      code: A519
      source: matweb-4130
      where: Key Words line, ASTM A519
    - system: AMS
      code: '6350'
      source: aircraft-4130
      where: Specifications list, AMS 6350 Sheet / Plate
    - system: AMS
      code: '6360'
      source: matweb-4130
      where: Key Words line, AMS 6360
    - system: AMS
      code: '6370'
      source: aircraft-4130
      where: Specifications list, AMS 6370 Bar
    - system: AMS
      code: '6345'
      source: aircraft-4130
      where: Specifications list, AMS 6345 Sheet / Plate, Normalised
    - system: AMS
      code: '6346'
      source: aircraft-4130
      where: Specifications list, AMS 6346 Bar, Hardened & Tempered
    - system: AMS
      code: '6348'
      source: aircraft-4130
      where: Specifications list, AMS 6348 Bar
    - system: AMS
      code: '6371'
      source: aircraft-4130
      where: Specifications list, AMS 6371 Tube
    - system: AMS
      code: '6356'
      source: matweb-4130
      where: Key Words line, AMS 6356
    - system: AMS
      code: '6361'
      source: matweb-4130
      where: Key Words line, AMS 6361
    - system: AMS
      code: '6372'
      source: matweb-4130
      where: Key Words line, AMS 6372
    - system: AMS
      code: '6373'
      source: matweb-4130
      where: Key Words line, AMS 6373
    - system: MIL
      code: MIL-S-6758
      source: aircraft-4130
      where: Specifications list, MIL-S-6758
    - system: MIL
      code: MIL-S-18729
      source: aircraft-4130
      where: Specifications list, MIL-S-18729
    - system: MIL
      code: MIL-T-67366
      source: aircraft-4130
      where: Specifications list, MIL-T-67366
    - system: MIL
      code: MIL-S-16974
      source: matweb-4130
      where: Key Words line, MIL SPEC MIL-S-16974
    - system: SAE
      code: J412
      source: matweb-4130
      where: Key Words line, SAE J412
    - system: SAE
      code: J770
      source: matweb-4130
      where: Key Words line, SAE J770
    - system: EN
      code: '1.7218'
      note: nearest equivalent
      source: saarstahl-25crmo4
      where: 'Header: Werkstoff-Nr. 1.7218 on the 25CrMo4 datasheet'
    - system: EN name
      code: 25CrMo4
      note: nearest equivalent
      source: saarstahl-25crmo4
      where: 'Page title: Saarstahl - 25CrMo4'
    - system: AFNOR
      code: 25 CD 4
      source: matweb-4130
      where: Key Words line, AFNOR 25 CD 4 (France)
    - system: BS
      code: CDS 110
      source: matweb-4130
      where: Key Words line, B.S. CDS 110 (UK)
    - system: SS
      code: 14 2225
      source: matweb-4130
      where: Key Words line, SS14 2225 (Sweden)
    - system: Trade name
      code: Chromoly
      source: materialwelding-4130
      where: 'Heading: AISI 4130 Steel aka Chromoly Steel'
tags:
  environments:
    - launch
  stresses: []
  applications:
    - propulsion-and-tanks
    - structures
    - mechanisms
properties:
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, quenched and tempered, temper about 635 C
    value: 820
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1144 K (about 871 C) for 120 min, oil quench, temper 908 K (about 635 C) for 120 min, air cool'
      strength_level: row 4130 [8] of Table 1.1.3
      test: test temperature and environment not stated in Table 1.1.3
    method: Table 1.1.3 as printed, Su column
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [8] row, Su column
  - benchmark: yield_strength
    label: Yield strength (Sy), quenched and tempered, temper about 635 C
    value: 635
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1144 K (about 871 C) for 120 min, oil quench, temper 908 K (about 635 C) for 120 min, air cool'
      strength_level: row 4130 [8] of Table 1.1.3
      test: test temperature and environment not stated in Table 1.1.3
    method: Table 1.1.3 as printed, Sy column (Sy is the yield strength as the report names it)
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [8] row, Sy column
  - benchmark: reduction_of_area
    label: Reduction of area, quenched and tempered, temper about 635 C
    value: 67
    unit: '%'
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1144 K (about 871 C) for 120 min, oil quench, temper 908 K (about 635 C) for 120 min, air cool'
      strength_level: row 4130 [8] of Table 1.1.3
    method: Table 1.1.3 as printed, RA column
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [8] row, RA column
  - benchmark: yield_strength
    label: Yield strength (Sy), quenched and tempered, lower strength level
    value: 1050
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1116 K, water quench, temper between 523 K and 813 K (about 250 C to 540 C) for 120 min'
      strength_level: lower of the two Sy levels printed for 4130 [6, 7]
      test: not stated in Table 1.1.3
    method: Table 1.1.3 as printed; the two strength levels share one heat-treatment cell, and Figure 3.2.2.1 spans 1050 to 1330 MPa
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [6, 7] rows, first Sy value
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, quenched and tempered, lower strength level
    value: 1140
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1116 K, water quench, temper between 523 K and 813 K (about 250 C to 540 C) for 120 min'
      strength_level: lower of the two strength levels printed for 4130 [6, 7]
      test: not stated in Table 1.1.3
    method: Table 1.1.3 as printed, Su column, paired with the first Sy value
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [6, 7] rows, first Su value
  - benchmark: yield_strength
    label: Yield strength (Sy), quenched and tempered, high strength level
    value: 1330
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1116 K, water quench, temper between 523 K and 813 K (about 250 C to 540 C) for 120 min'
      strength_level: high strength level; Section 3.2.2 calls 1330 MPa high strength
      test: not stated in Table 1.1.3
    method: Table 1.1.3 as printed, second Sy value for 4130 [6, 7]
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [6, 7] rows, second Sy value; Section 3.2.2 text
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, quenched and tempered, high strength level
    value: 1600
    unit: MPa
    scope: material
    conditions:
      condition: 'quenched and tempered: austenitize 1116 K, water quench, temper between 523 K and 813 K (about 250 C to 540 C) for 120 min'
      strength_level: high strength level
      test: not stated in Table 1.1.3
    method: Table 1.1.3 as printed, second Su value for 4130 [6, 7]
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [6, 7] rows, second Su value
  - benchmark: threshold_stress_intensity_factor
    label: Threshold stress-intensity factor KTH in hydrogen gas, 21 MPa H2
    value: 88
    unit: MPa√m
    scope: material
    conditions:
      environment: high-pressure hydrogen gas, 21 MPa H2
      temperature: 286 K (about 13 C)
      heat_treatment: 'same reference and yield strength as the Table 1.1.3 row for 4130 [8]: austenitize 1144 K, oil quench, temper 908 K'
      yield_strength: 635 MPa
    method: Table 3.2.2.1 as printed, 4130 [8] row
    status: ground
    source: sandia-1211
    where: Table 3.2.2.1, 4130 [8] row, 21 MPa H2 line
  - benchmark: threshold_stress_intensity_factor
    label: Threshold stress-intensity factor KTH in hydrogen gas, 41 MPa H2
    value: 68
    unit: MPa√m
    scope: material
    conditions:
      environment: high-pressure hydrogen gas, 41 MPa H2
      temperature: 286 K (about 13 C)
      heat_treatment: 'same reference and yield strength as the Table 1.1.3 row for 4130 [8]: austenitize 1144 K, oil quench, temper 908 K'
      yield_strength: 635 MPa
    method: Table 3.2.2.1 as printed, 4130 [8] row
    status: ground
    source: sandia-1211
    where: Table 3.2.2.1, 4130 [8] row, 41 MPa H2 line
  - benchmark: threshold_stress_intensity_factor
    label: Threshold stress-intensity factor KTH in hydrogen gas, 62 MPa H2
    value: 45
    unit: MPa√m
    scope: material
    conditions:
      environment: high-pressure hydrogen gas, 62 MPa H2
      temperature: 286 K (about 13 C)
      heat_treatment: 'same reference and yield strength as the Table 1.1.3 row for 4130 [8]: austenitize 1144 K, oil quench, temper 908 K'
      yield_strength: 635 MPa
    method: Table 3.2.2.1 as printed, 4130 [8] row
    status: ground
    source: sandia-1211
    where: Table 3.2.2.1, 4130 [8] row, 62 MPa H2 line
  - benchmark: threshold_stress_intensity_factor
    label: Threshold stress-intensity factor KTH in hydrogen gas, 69 MPa H2
    value: 32
    unit: MPa√m
    scope: material
    conditions:
      environment: high-pressure hydrogen gas, 69 MPa H2
      temperature: 286 K (about 13 C)
      heat_treatment: 'same reference and yield strength as the Table 1.1.3 row for 4130 [8]: austenitize 1144 K, oil quench, temper 908 K'
      yield_strength: 635 MPa
    method: Table 3.2.2.1 as printed, 4130 [8] row
    status: ground
    source: sandia-1211
    where: Table 3.2.2.1, 4130 [8] row, 69 MPa H2 line
  - benchmark: threshold_stress_intensity_factor
    label: Threshold stress-intensity factor KTH in hydrogen gas, 97 MPa H2
    value: 52
    unit: MPa√m
    scope: material
    conditions:
      environment: high-pressure hydrogen gas, 97 MPa H2
      temperature: 286 K (about 13 C)
      heat_treatment: 'same reference and yield strength as the Table 1.1.3 row for 4130 [8]: austenitize 1144 K, oil quench, temper 908 K'
      yield_strength: 635 MPa
    method: Table 3.2.2.1 as printed, 4130 [8] row; this value is above the 69 MPa value, as printed
    status: ground
    source: sandia-1211
    where: Table 3.2.2.1, 4130 [8] row, 97 MPa H2 line
  - benchmark: fracture_toughness
    label: Fracture toughness KIc, quenched and tempered, temper about 635 C
    value: 125
    unit: MPa√m
    scope: material
    note: 'Sandia footnote: not reported as a standardised KIc measurement.'
    conditions:
      condition: 'quenched and tempered: austenitize 1144 K (about 871 C) for 120 min, oil quench, temper 908 K (about 635 C) for 120 min, air cool'
      basis: KIc column of Table 1.1.3, row 4130 [8]
    method: Table 1.1.3 as printed; the report footnote says not reported as standardised KIc
    status: ground
    source: sandia-1211
    where: Table 1.1.3, 4130 [8] row, KIc column, footnote marked with an asterisk
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, normalised at 870 C (1600 F)
    value: 670
    unit: MPa
    scope: material
    conditions:
      condition: normalised at 870 C (1600 F), as the MatWeb record title states
      test: test temperature not stated
    method: MatWeb datasheet printout, Mechanical Properties rows, metric value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Tensile Strength Ultimate, 670 MPa (97200 psi)
  - benchmark: yield_strength
    label: Yield strength, normalised at 870 C (1600 F)
    value: 435
    unit: MPa
    scope: material
    conditions:
      condition: normalised at 870 C (1600 F), as the MatWeb record title states
      test: test temperature not stated
    method: MatWeb datasheet printout, Mechanical Properties rows, metric value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Tensile Strength Yield, 435 MPa (63100 psi)
  - benchmark: elongation
    label: Elongation at break, normalised at 870 C (1600 F)
    value: 25.5
    unit: '%'
    scope: material
    conditions:
      condition: normalised at 870 C (1600 F), as the MatWeb record title states
      gauge: 50 mm, as printed
    method: MatWeb datasheet printout, Mechanical Properties rows, value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Elongation at Break, 25.5 % in 50 mm
  - benchmark: reduction_of_area
    label: Reduction of area, normalised at 870 C (1600 F)
    value: 60
    unit: '%'
    scope: material
    conditions:
      condition: normalised at 870 C (1600 F), as the MatWeb record title states
    method: MatWeb datasheet printout, Mechanical Properties rows, value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Reduction of Area, 60 %
  - benchmark: hardness_brinell
    label: Hardness, Brinell, normalised at 870 C (1600 F)
    value: 197
    unit: HB
    scope: material
    conditions:
      condition: normalised at 870 C (1600 F), as the MatWeb record title states
    method: MatWeb datasheet printout, Brinell hardness row as printed (the other scales are converted by MatWeb)
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Hardness, Brinell, 197
  - benchmark: density
    value: 7.85
    unit: g/cc
    scope: material
    conditions:
      basis: physical properties table; no temperature stated; record titled normalised at 870 C
    method: MatWeb physical properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Physical Properties, Density, 7.85 g/cc (0.284 lb/in3)
  - benchmark: elastic_modulus
    label: Modulus of elasticity
    value: 205
    unit: GPa
    scope: material
    conditions:
      basis: marked Typical for steel on the datasheet; no temperature stated
    method: MatWeb mechanical properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Modulus of Elasticity, 205 GPa (29700 ksi)
  - benchmark: bulk_modulus
    value: 160
    unit: GPa
    scope: material
    conditions:
      basis: marked Typical for steel on the datasheet; no temperature stated
    method: MatWeb mechanical properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Bulk Modulus, 160 GPa (23200 ksi)
  - benchmark: shear_modulus
    value: 80
    unit: GPa
    scope: material
    conditions:
      basis: marked Typical for steel on the datasheet; no temperature stated
    method: MatWeb mechanical properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Shear Modulus, 80.0 GPa (11600 ksi)
  - benchmark: poissons_ratio
    value: 0.29
    unit: '-'
    scope: material
    conditions:
      basis: marked Calculated on the datasheet; no temperature stated
    method: MatWeb mechanical properties row, value as printed with the Calculated comment
    status: calculated
    source: matweb-4130
    where: Mechanical Properties, Poissons Ratio, 0.29 (comment Calculated)
  - benchmark: impact_energy
    label: Izod impact energy
    value: 87
    unit: J
    scope: material
    conditions:
      test: Izod
      temperature: not stated on the datasheet
      condition: record titled normalised at 870 C
    method: MatWeb mechanical properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Izod Impact, 87.0 J (64.2 ft-lb)
  - benchmark: machinability
    label: Machinability rating (AISI 1212 = 100 %)
    value: 70
    unit: '%'
    scope: material
    conditions:
      condition: annealed and cold drawn
      reference: AISI 1212 steel is taken as 100 %
    method: MatWeb mechanical properties row, value as printed with its basis
    status: ground
    source: matweb-4130
    where: Mechanical Properties, Machinability, 70 %
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 100 C (212 F)
    value: 42.7
    unit: W/m-K
    scope: material
    conditions:
      temperature: 100 C (212 F)
      printed_alternative: 296 BTU-in/hr-ft2-F
    method: MatWeb thermal properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Thermal Properties, Thermal Conductivity, 42.7 W/m-K (296 BTU-in/hr-ft2-F) at 100 C
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 1200 C (2190 F)
    value: 30.1
    unit: W/m-K
    scope: material
    conditions:
      temperature: 1200 C (2190 F)
      printed_alternative: 209 BTU-in/hr-ft2-F
    method: MatWeb thermal properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Thermal Properties, Thermal Conductivity, 30.1 W/m-K at 1200 C
  - benchmark: specific_heat
    label: Specific heat capacity at 100 C or above
    value: 0.477
    unit: J/g-°C
    scope: material
    conditions:
      temperature: 100 C (212 F) or above
      printed_alternative: 0.114 BTU/lb-F
    method: MatWeb thermal properties row, metric value as printed
    status: ground
    source: matweb-4130
    where: Thermal Properties, Specific Heat Capacity, 0.477 J/g-C at 100 C or above
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 20 C, hardened and tempered specimen
    value: 0.0000223
    unit: ohm-cm
    scope: material
    conditions:
      condition: specimen hardened and tempered
      temperature: 20 C (68 F)
    method: MatWeb electrical properties row, value as printed
    status: ground
    source: matweb-4130
    where: Electrical Properties, Electrical Resistivity, 0.0000223 ohm-cm at 20.0 C, specimen hardened and tempered
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, hardened and tempered bar (AMS 6346), temper not stated
    value: 125
    unit: ksi
    scope: material
    conditions:
      condition: hardened and tempered bar, AMS 6346; temper temperature not stated
    method: Typical Mechanical Properties table as printed; the table header gives ksi
    status: ground
    source: aircraft-4130
    where: Typical Mechanical Properties table, Bar AMS 6346, Hardened and Tempered, Tensile Strength ksi 125
  - benchmark: yield_strength
    label: Yield strength, hardened and tempered bar (AMS 6346), temper not stated
    value: 100
    unit: ksi
    scope: material
    conditions:
      condition: hardened and tempered bar, AMS 6346; temper temperature not stated
    method: Typical Mechanical Properties table as printed; the table header gives ksi
    status: ground
    source: aircraft-4130
    where: Typical Mechanical Properties table, Bar AMS 6346, Hardened and Tempered, Yield Strength ksi 100
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, cold drawn tube (AMS 6371)
    value: 95
    unit: ksi
    scope: material
    conditions:
      condition: cold drawn tube, AMS 6371
    method: Typical Mechanical Properties table as printed; the table header gives ksi
    status: ground
    source: aircraft-4130
    where: Typical Mechanical Properties table, Tube AMS 6371, Cold Drawn, Tensile Strength ksi 95
  - benchmark: yield_strength
    label: Yield strength, cold drawn tube (AMS 6371)
    value: 70
    unit: ksi
    scope: material
    conditions:
      condition: cold drawn tube, AMS 6371
    method: Typical Mechanical Properties table as printed; the table header gives ksi
    status: ground
    source: aircraft-4130
    where: Typical Mechanical Properties table, Tube AMS 6371, Cold Drawn, Yield Strength ksi 70
  - benchmark: hardness_brinell
    label: Hardness, annealed bar (AMS 6370), maximum
    value: 29
    bound: upper
    unit: HB
    scope: material
    conditions:
      condition: annealed bar, AMS 6370
    method: Typical Mechanical Properties table as printed, 29HB Max
    status: ground
    source: aircraft-4130
    where: Typical Mechanical Properties table, Bar AMS 6370, Annealed, Hardness 29HB Max
  - benchmark: hardness_rockwell_c
    label: Hardness, annealed sheet (AMS 6350), maximum
    value: 25
    bound: upper
    unit: HRC
    scope: material
    conditions:
      condition: annealed sheet, AMS 6350
    method: Typical Mechanical Properties table as printed, printed as less than 25 HRC
    status: ground
    source: aircraft-4130
    where: Typical Mechanical Properties table, Sheet AMS 6350, Annealed, Hardness less than 25 HRC
  - benchmark: hardness_rockwell_c
    label: Hardness, round bar as usually supplied (quenched and tempered)
    value: 18
    value_high: 22
    bound: range
    unit: HRC
    scope: material
    conditions:
      condition: round bar, usually supplied quenched and tempered, as the article states
    method: Range as printed in the Material Welding article; no test method is printed
    status: ground
    source: materialwelding-4130
    where: 'AISI 4130 Chemical Properties introduction: usually quenched and tempered, hardness 18-22 HRC'
  - benchmark: melting_point
    label: Melting point
    value: 2610
    unit: F
    scope: material
    conditions:
      basis: physical properties table; no condition stated
    method: Titanium Industries physical properties table, Melting Point (F) as printed
    status: ground
    source: titanium-4130
    where: Table 2, PHYSICAL PROPERTIES, Melting Point (°F), 2610
  - benchmark: cte
    label: Coefficient of thermal expansion (printed per degree F)
    value: 0.0000062
    unit: 1/F
    scope: material
    conditions:
      temperature: not stated in the table
    method: Titanium Industries physical properties table, Thermal expansion (1/F) as printed; the table prints 0.00000620
    status: ground
    source: titanium-4130
    where: Table 2, PHYSICAL PROPERTIES, Thermal expansion (1/°F), 0.00000620
  - benchmark: electrical_conductivity
    label: Electrical conductivity
    value: 7.73
    unit: '% IACS'
    scope: material
    conditions:
      basis: physical properties table; no temperature or condition stated
    method: Titanium Industries physical properties table, Electrical conductivity (% IACS) as printed
    status: ground
    source: titanium-4130
    where: Table 2, PHYSICAL PROPERTIES, Electrical conductivity (% IACS), 7.73
corrosion:
  - environment: Aerated aqueous NaCl, CaCl2 and sodium bicarbonate solution at room temperature, corrosion-fatigue at 1 Hz and R = 0.1
    headline: Salt solution cut the fatigue life of AISI 4130 at every strength level tested, from 837 to 1846 MPa.
    effect: 'All specimens tested in the salt solution failed in less than 150,000 cycles, while some tested in air ran out beyond 10^6 cycles. The salt solution lowered the fatigue limit at each strength level. The thesis ties the loss to martensite: the more martensite, the larger the drop. The rating severe is an assistant judgement from these findings.'
    rating: severe
    conditions:
      solution: aqueous NaCl, CaCl2 and sodium bicarbonate
      temperature: room temperature, constant aeration
      loading: 1 Hz, stress ratio R = 0.1
      strength_levels: six levels, 837 to 1846 MPa (121 to 268 ksi)
    source: gatech-cf
    where: Abstract, findings paragraph (the 10^6 is a superscript in the abstract)
  - environment: Hydrogen gas at 21 to 97 MPa and 286 K, and low-pressure hydrogen at 0.08 MPa
    headline: Hydrogen gas lowers the threshold stress intensity of quenched and tempered 4130, from 88 MPa√m at 21 MPa H2 to 32 MPa√m at 69 MPa H2.
    effect: The Sandia reference says hydrogen gas lowers fracture toughness and makes Cr-Mo steels susceptible to crack extension under static loading. For 4130 the threshold falls by a factor of three as yield strength rises from 1050 to 1330 MPa in low-pressure hydrogen, and it rises 40 to 50 percent when the temperature is 50 K above ambient. The printed value at 97 MPa H2 (52 MPa√m) is above the 69 MPa value, and the report prints it that way. The rating severe is an assistant judgement.
    rating: severe
    conditions:
      temperature: 286 K (about 13 C) for the Table 3.2.2.1 values
      pressure: 21, 41, 62, 69 and 97 MPa H2
      heat_treatment: austenitize 1144 K, oil quench, temper 908 K (row 4130 [8])
    source: sandia-1211
    where: Section 1 and Section 3.2.2 text; Table 3.2.2.1, 4130 [8] row; Figure 3.2.2.1
  - environment: Atmosphere, general (no test conditions printed)
    headline: Titanium Industries describes AISI 4130 as having good atmospheric resistance; no corrosion rate is printed.
    effect: The supplier says the grade has good atmospheric resistance and good strength at moderately high temperatures. The page gives no exposure time, site or rate, so this is a supplier statement, not a measured result.
    rating: unknown
    conditions:
      basis: supplier statement; no test conditions printed
    source: titanium-4130
    where: Introduction paragraph, Alloy Steel 4130 | UNS G41300
risks:
  hazards:
    - text: 'PubChem aggregated GHS for elemental chromium (signal word Danger): H317 (20.7%), H319 (19.1%) and H334 (20.3%) are reported codes above 10%. 50% (1202 of 2404) of reports say it does not meet GHS hazard criteria. The data cover the element, not the alloy.'
      ghs:
        - H317
        - H319
        - H334
      source: pubchem-chromium
      where: Safety and Hazards, GHS Classification (CID 23976)
    - text: 'PubChem aggregated GHS for elemental molybdenum (signal word Danger): H228 flammable solid (30%), H361 suspected of damaging fertility or the unborn child (29.5%) and H225 (11.6%). 57.4% (874 of 1523) of reports say it does not meet GHS hazard criteria. The data cover the element, not the alloy.'
      ghs:
        - H228
        - H361
        - H225
      source: pubchem-molybdenum
      where: Safety and Hazards, GHS Classification (CID 23932)
    - text: 'PubChem aggregated GHS for elemental manganese (signal word Danger): H228 (11.6%), H319 (14.8%), H411 (10.9%) and H412 (10.8%), with H360 (may damage fertility or the unborn child) and H372 (causes damage to organs through prolonged or repeated exposure) also listed. 46.1% (1429 of 3101) of reports say it does not meet GHS hazard criteria. The data cover the element, not the alloy.'
      ghs:
        - H228
        - H319
        - H360
        - H372
        - H411
        - H412
      source: pubchem-manganese
      where: Safety and Hazards, GHS Classification (CID 23930)
  failure_risks:
    - mode: Hydrogen embrittlement under static load
      trigger: Hydrogen gas at 21 to 97 MPa and 286 K, and low-pressure hydrogen at 0.08 MPa
      consequence: The threshold stress intensity of the 635 MPa yield strength level fell from 88 MPa√m at 21 MPa H2 to 32 MPa√m at 69 MPa H2. The report ties the loss to yield strength, and says limiting yield strength improves resistance. The threshold also rises 40 to 50 percent when the temperature is 50 K above ambient and falls 25 to 30 percent when it is 70 K below ambient.
      severity: high
      source: sandia-1211
      where: Table 3.2.2.1, 4130 [8] row; Section 3.2.2 (effect of yield strength and temperature)
    - mode: Hydrogen cracking in welds
      trigger: Welding 4130 without the recommended preheat, with unbaked consumables, or with fast cooling
      consequence: Material Welding says 4130 is particularly prone to hydrogen cracking, which the filler metal and slow cooling can reduce.
      severity: high
      source: materialwelding-4130
      where: Weldability section (hydrogen cracking paragraph)
    - mode: Corrosion fatigue in salt solutions
      trigger: Aerated aqueous NaCl and CaCl2 solution under cyclic loading (1 Hz, R = 0.1)
      consequence: Every specimen tested in the salt solution failed in less than 150,000 cycles, and the salt solution lowered the fatigue limit at each strength level tested.
      severity: high
      source: gatech-cf
      where: Abstract, findings paragraph
    - mode: Loss of tempering effect in post-weld heat treatment
      trigger: Post-weld heat treatment at a temperature above the tempering temperature
      consequence: A high PWHT temperature destroys the tempering effect in the base material.
      severity: moderate
      source: materialwelding-4130
      where: 4130 Heat Treatment section
  side_effects: []
  handling:
    - text: Preheat to about 200 to 300 C (400 to 570 F) before welding. Use the upper end for sections thicker than 25 mm or when working in a cold environment. Slower cooling after welding also reduces the risk of cracking.
      source: materialwelding-4130
      where: Weldability and Preheat sections
    - text: Use fully baked welding consumables and an appropriate filler. ER80S-D2 is the recommended filler; ER70S-2 and ER70S-6 are alternatives with slightly lower toughness.
      source: materialwelding-4130
      where: Welding consumables and filler questions
    - text: Stress relieve parts thicker than 3 mm (0.120 in) at about 600 C, holding about one hour per inch of thickness, and keep the temperature below the tempering temperature.
      source: materialwelding-4130
      where: Heat Treatment section and stress relief question
    - text: Quote the heat-treatment condition with every strength value. The normalised, annealed, hardened and tempered, cold drawn and quenched-and-tempered rows in this file come from different heat treatments.
      source: aircraft-4130
      where: Typical Mechanical Properties table and MatWeb record title
  mitigations:
    - text: Limit the yield strength of the chosen condition. Sandia states that limiting steel yield strength can improve resistance to hydrogen embrittlement, and the threshold falls as yield strength rises.
      source: sandia-1211
      where: Section 1, General (text); Figure 3.2.2.1 and Section 3.2.2
    - text: Avoid hydrogen cracking by using fully baked welding consumables and an appropriate filler, with preheat and slow cooling after welding.
      source: materialwelding-4130
      where: Weldability and Consumables sections
uses:
  - application: propulsion-and-tanks
    device: Solid rocket booster case
    example: NASA's list of heritage launch-vehicle materials names 4130 among the solid rocket booster case materials, with D6AC, 18% nickel maraging steel and titanium.
    source: nasa-srb
    where: Launch Vehicle Structures and Solid Rocket Boosters, Case Materials list
  - application: structures
    device: Aircraft tube, sheet and bar for military and commercial aircraft
    example: Aircraft Materials lists 4130 tube to AMS 6371, bar to AMS 6346 and sheet to AMS 6350, and names military and commercial aircraft among its applications.
    source: aircraft-4130
    where: Applications list; Specifications list
  - application: structures
    device: Oil and gas wellhead and Christmas tree parts
    example: Material Welding says quenched and tempered 4130 round bar is used in oil and gas drilling and production components, such as wellhead and Christmas tree parts.
    source: materialwelding-4130
    where: AISI 4130 Chemical Properties introduction and the oil and gas sentence
  - application: mechanisms
    device: Machine tool components and forged valve bodies and pumps
    example: Aircraft Materials lists machine tools among 4130 applications, and Titanium Industries lists forged valve bodies and pumps.
    source: aircraft-4130
    where: Applications list
supply:
  - subject: Chromium
    abundance: 'World resources are greater than 12 billion tons of shipping-grade chromite, 95 percent of chromium resources in Kazakhstan and southern Africa (USGS). US net import reliance was 79 percent of apparent consumption in 2025e. Chromite imports in 2021 to 2024 came from South Africa (96%), Turkey (3%) and other (1%). 2025e mine production as printed: South Africa 23,000; Turkey 9,000; Kazakhstan 7,000; India 3,000; Brazil 2,000; Zimbabwe 2,000; Finland 1,900; world total 51,000 (rounded). Producer shares are not printed by USGS and are not calculated here.'
    producers:
      - country: South Africa
        year: 2025
      - country: Turkey
        year: 2025
      - country: Kazakhstan
        year: 2025
      - country: India
        year: 2025
      - country: Brazil
        year: 2025
      - country: Zimbabwe
        year: 2025
      - country: Finland
        year: 2025
    critical_lists: []
    recycling: Recycled chromium in reported stainless-steel scrap receipts accounted for 21 percent of apparent consumption in 2025 (USGS).
    substitutes:
      - Chromium has no substitute in stainless steel, the leading end use, or in superalloys (USGS). Chromium-containing scrap can substitute for ferrochromium in some metallurgical uses.
    source: usgs-chromium-2026
    where: Salient Statistics; Import Sources (2021-24); Recycling; World Mine Production and Reserves (2025e); World Resources; Substitutes
  - subject: Molybdenum
    abundance: 'Identified resources are about 5.4 million tons in the United States and about 20 million tons in the rest of the world (USGS). World reserves were 17,000 thousand metric tons. Molybdenum is used principally as an alloying agent in cast iron and steel. The United States is a net exporter (E in the USGS table, 2021 to 2025e). In 2025e, China, Chile, the United States, Peru and Mexico account for 90 percent of world production (USGS). 2025e mine production as printed: China 97,000; Chile 42,000; United States 40,000; Peru 39,000; Mexico 17,000; world total 260,000 (rounded). The Government of China imposed export controls on molybdenum powders in February 2025.'
    producers:
      - country: China
        year: 2025
      - country: Chile
        year: 2025
      - country: United States
        year: 2025
      - country: Peru
        year: 2025
      - country: Mexico
        year: 2025
    critical_lists: []
    recycling: Molybdenum is recycled from catalysts, ferrous scrap and superalloy scrap. Recycled molybdenum in new and old steel and other scrap may be as much as 30 percent of the apparent supply (USGS).
    substitutes:
      - There is little substitution for molybdenum in steels and cast irons. Potential substitutes in alloy steels include boron, chromium, niobium (columbium) and vanadium (USGS).
    source: usgs-molybdenum-2026
    where: Salient Statistics; Recycling; Events, Trends and Issues; World Mine Production and Reserves (2025e); World Resources; Substitutes
media: []
documents:
  - title: 'Aircraft Materials: 4130 (AMS 6345 / AMS 6346 / AMS 6350) chrome-moly aircraft steel technical data sheet'
    type: datasheet
    url: https://aircraftmaterials.com/data/alstst/4130.html
  - title: 'MatWeb: AISI 4130 Steel, normalized at 870 C (1600 F), datasheet printout (copy hosted on quickparts.com)'
    type: datasheet
    url: https://quickparts.com/wp-content/uploads/2024/05/Steel-4130.pdf
  - title: 'Titanium Industries: Alloy Steel 4130 (UNS G41300) page'
    type: datasheet
    url: https://titanium.com/alloys/alloy-steels/alloy-steel-4130/
  - title: 'Technical Reference on Hydrogen Compatibility of Materials: Low-Alloy Ferritic Steels, Tempered Fe-Cr-Mo Alloys (code 1211), Sandia National Laboratories'
    type: report
    url: https://www.sandia.gov/app/uploads/sites/158/2021/12/1211TechRef_FeCrMo_T.pdf
    year: 2005
  - title: 'NASA NTRS 20190020090: Heritage Materials for Launch Vehicles and Spacecraft'
    type: report
    url: https://ntrs.nasa.gov/api/citations/20190020090/downloads/20190020090.pdf
  - title: 'Material Welding: Welding 4130 Steel: Complete Guidelines'
    type: report
    url: https://materialwelding.com/how-to-weld-aisi-4130-steel/
  - title: 'Saarstahl: Werkstoff-Datenblatt 25CrMo4 (1.7218)'
    type: datasheet
    url: https://www.saarstahl.com/app/uploads/2024/03/20160318114702-25CrMo4-.pdf
  - title: 'Evins, J. L. (2004): Dependence of Strength on Corrosion-Fatigue Resistance of AISI 4130 Steel, Georgia Tech MS thesis'
    type: paper
    url: https://repository.gatech.edu/entities/publication/98a0585f-9939-476a-b8e7-986068df1a43
    year: 2004
  - 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
  - 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
  - title: 'PubChem: Manganese (CID 23930), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23930/JSON/?heading=GHS+Classification
  - 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
gaps:
  - 'identity.cas, crystal_system and space_group: not printed by any source read in this run. A CAS number does not apply to a steel mixture, and no crystal structure source was read for the alloy.'
  - No standard text was read for SAE J404, AMS 6350, AMS 6360, ASTM A519, A322, A331 or MIL-S-6758. The codes are as the cited pages print them.
  - Composition limits disagree between sources. Aircraft Materials prints phosphorus and sulfur at 0.025 max (silicon 0.15 to 0.35 for bar and tube, 0.20 to 0.35 for sheet). MatWeb prints phosphorus 0.035 max, sulfur 0.040 max and silicon 0.15 to 0.30. Material Welding prints sulfur 0.035 max and phosphorus 0.025 max. The recipe uses the allowable ranges in Sandia Table 1.1.1 (phosphorus 0.035 max, sulfur 0.040 max).
  - No annealed tensile or yield strength was found. AMS 6370 bar and AMS 6350 sheet give hardness only (29 HB maximum and less than 25 HRC).
  - Aircraft Materials prints elongation without a unit, and it prints the normalised sheet hardness without a unit. Neither is recorded. Its tube hardness is printed as less than 25 with no unit, and it is not recorded either.
  - Titanium Industries prints density 0.284 and specific heat 0.114 with no unit, so neither is recorded. Its yield, tensile, elongation and hardness ranges combine several conditions, so they are not recorded.
  - Material Welding prints tensile 560 MPa and yield 460 MPa with no condition, so they are not recorded. ICAST Alloys prints tensile 480 to 1379 MPa across annealing, normalising and hardening rows, so it is not recorded.
  - Sandia gives two strength levels for 4130 [6, 7] under one heat-treatment cell (tempering between 523 K and 813 K). The file records them as lower and high levels, following the text of Section 3.2.2. The report gives no temper temperature for each level.
  - Sandia's 4130 rows are all quenched and tempered. The report has no hydrogen tensile or notched-tensile data for 4130; its notched tables cover 4140 only. The 4130 hydrogen data are threshold values from one high-pressure study and one low-pressure study.
  - Sandia's 4130 chemistry in Table 1.1.2 (test heats) is not used for the recipe, which uses the allowable ranges in Table 1.1.1.
  - 'Corrosion: no chloride immersion rate, acid immersion rate or atmospheric test value for 4130 was read in this run. The 2020 welded-joint paper (garuda.kemdikbud.go.id/documents/detail/2140279) and the University of Southern Queensland heat-treatment paper did not respond to the fetch.'
  - 'Weldability: the preheat, filler and stress-relief values come from Material Welding, a commercial guide, not from a welding procedure specification (AWS D1.1 or ASME IX). Check them against a qualified welding procedure before use.'
  - 'Critical minerals: the USGS 2025 critical minerals page returned HTTP 403 in this run, so no critical-list entry is recorded for chromium or molybdenum.'
  - 'Supply: USGS prints tonnage, not country shares, so producer shares are not calculated here. The 2025e tonnage is in the abundance text.'
  - 'Designations not recorded: JIS SCM430 is printed by MakeItFrom, which returned HTTP 403. MatWeb prints JIS SCM 2 and JIS SCCrM 1 as key words, but neither is confirmed as the same steel. a guessed Elgin 4130 fact sheet URL returned HTTP 404.'
  - 'Designations as nearest equivalents: Saarstahl''s 25CrMo4 datasheet (1.7218) gives a typical carbon of 0.25 against 0.28 to 0.33 for AISI 4130, so 25CrMo4 and 1.7218 are marked nearest equivalent, not the same grade.'
  - No safety data sheet for the 4130 bar was read in this run. The hazard entries are PubChem records for elemental chromium, molybdenum and manganese, and welding fume hazards of the steel itself are not sourced.
  - No source in this run compares 4130 with 4140 head to head. The Sandia tables list both grades, but their heat treatments differ, so no 4140 value is used in this file.
  - 'Non-canonical benchmark names used: hardness_brinell, hardness_rockwell_c, impact_energy, machinability, electrical_conductivity, threshold_stress_intensity_factor, fracture_toughness, reduction_of_area.'
  - NASA's heritage list names 4130 for solid rocket booster cases but gives no 4130 data (wall thickness, yield strength or flight history). Launch-vehicle use is recorded as the list entry only.
sources:
  aircraft-4130:
    title: 'Aircraft Materials: 4130 (AMS 6345 / AMS 6346 / AMS 6350) chrome-moly aircraft steel technical data sheet'
    id: AISI 4130 Aircraft Steel
    url: https://aircraftmaterials.com/data/alstst/4130.html
    kind: datasheet
    license: supplier web page, cited not reproduced
  matweb-4130:
    title: 'MatWeb: AISI 4130 Steel, normalized at 870 C (1600 F), datasheet printout'
    id: MatWeb matguid e1ccebe90cf94502b35c2a4745f63593 (copy on quickparts.com)
    url: https://quickparts.com/wp-content/uploads/2024/05/Steel-4130.pdf
    kind: datasheet
    license: MatWeb terms of use, cited not reproduced
  titanium-4130:
    title: 'Titanium Industries: Alloy Steel 4130 (UNS G41300) page with physical properties table'
    id: Alloy Steel 4130 | UNS G41300
    url: https://titanium.com/alloys/alloy-steels/alloy-steel-4130/
    kind: datasheet
    license: supplier web page, cited not reproduced
  sandia-1211:
    title: 'Technical Reference on Hydrogen Compatibility of Materials: Low-Alloy Ferritic Steels, Tempered Fe-Cr-Mo Alloys (code 1211)'
    id: Sandia National Laboratories, code 1211, December 8, 2005
    url: https://www.sandia.gov/app/uploads/sites/158/2021/12/1211TechRef_FeCrMo_T.pdf
    year: 2005
    kind: report
    license: US government report, public
  nasa-srb:
    title: 'NASA NTRS 20190020090: Heritage Materials for Launch Vehicles and Spacecraft'
    id: NTRS 20190020090
    url: https://ntrs.nasa.gov/api/citations/20190020090/downloads/20190020090.pdf
    kind: report
    license: NASA public document
  materialwelding-4130:
    title: 'Material Welding: Welding 4130 Steel: Complete Guidelines'
    id: AISI 4130 Steel aka Chromoly Steel guide
    url: https://materialwelding.com/how-to-weld-aisi-4130-steel/
    kind: web
    license: web article, cited not reproduced
  saarstahl-25crmo4:
    title: 'Saarstahl: Werkstoff-Datenblatt 25CrMo4 (1.7218)'
    id: 25CrMo4 / 1.7218
    url: https://www.saarstahl.com/app/uploads/2024/03/20160318114702-25CrMo4-.pdf
    kind: datasheet
    license: manufacturer datasheet, cited not reproduced
  gatech-cf:
    title: 'Evins, J. L. (2004): Dependence of Strength on Corrosion-Fatigue Resistance of AISI 4130 Steel, Georgia Tech MS thesis'
    id: hdl.handle.net/1853/5265
    url: https://repository.gatech.edu/entities/publication/98a0585f-9939-476a-b8e7-986068df1a43
    year: 2004
    kind: paper
    license: Georgia Tech repository record
  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
    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
    kind: database
    license: PubChem terms (public)
  pubchem-manganese:
    title: 'PubChem: Manganese (CID 23930), Safety and Hazards, GHS Classification'
    id: CID 23930
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23930/JSON/?heading=GHS+Classification
    kind: database
    license: PubChem terms (public)
  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)
license: CC-BY-4.0
updated: '2026-10-24'
review:
  status: draft
  method: assistant
  checked_values: 39
  unreachable: 0
  caveats: 3
  note: 'Read by an AI assistant on 2026-10-24 from pages fetched in this run. Each value is tied to its own condition. Caveats: the Sandia KIc is not a standardised measurement; the Sandia 4130 [6, 7] strength levels share one heat-treatment cell; the thermal expansion is printed per degree F. Not reached: a guessed Elgin 4130 fact sheet URL (HTTP 404), MakeItFrom (HTTP 403), Harris Products welding page (HTTP 403), Suppliersonline (HTTP 503), USGS critical minerals page (HTTP 403), two corrosion papers (no response).'
story:
  recipe:
    line: AISI 4130 is an iron-based, low-alloy chromium-molybdenum steel, not a stainless steel. Table 1.1.1 of the Sandia reference gives its allowable ranges as 0.28 to 0.33 carbon, 0.40 to 0.60 manganese, 0.15 to 0.35 silicon, 0.80 to 1.10 chromium and 0.15 to 0.25 molybdenum (wt%), with phosphorus at 0.035 max and sulfur at 0.040 max. Aircraft Materials says bar is vacuum degassed to meet magnetic particle inspection standards. Its strength comes from heat treatment (normalising, annealing, or quenching and tempering).
    parts:
      - name: Iron
        symbol: Fe
        share_note: balance (the rest)
        role: The matrix of the steel; heat treatment turns its structure from austenite to martensite and then to tempered martensite, or to ferrite and carbide when normalised or annealed.
        source: sandia-1211
        where: 'Table 1.1.1, row 4130; footnote: balance is Fe'
      - name: Carbon
        symbol: C
        share_percent: 0.28
        share_high: 0.33
        role: Sets how hard the steel can become when quenched; medium carbon gives the strength range.
        source: sandia-1211
        where: Table 1.1.1, row 4130
      - name: Manganese
        symbol: Mn
        share_percent: 0.4
        share_high: 0.6
        role: Deoxidiser and hardenability aid.
        source: sandia-1211
        where: Table 1.1.1, row 4130
      - name: Silicon
        symbol: Si
        share_percent: 0.15
        share_high: 0.35
        role: Deoxidiser.
        source: sandia-1211
        where: Table 1.1.1, row 4130
      - name: Chromium
        symbol: Cr
        share_percent: 0.8
        share_high: 1.1
        role: Adds hardenability and some corrosion resistance; the grade is still a low-alloy steel.
        source: sandia-1211
        where: Table 1.1.1, row 4130
      - name: Molybdenum
        symbol: Mo
        share_percent: 0.15
        share_high: 0.25
        role: Adds hardenability and strength at temperature.
        source: sandia-1211
        where: Table 1.1.1, row 4130
      - name: Phosphorus
        symbol: P
        share_note: max 0.035
        role: Impurity held low.
        source: sandia-1211
        where: Table 1.1.1, row 4130, maximum
      - name: Sulfur
        symbol: S
        share_note: max 0.040
        role: Impurity held low.
        source: sandia-1211
        where: Table 1.1.1, row 4130, maximum
  risk_groups:
    - title: For people
      level: 1
      verdict: Element data only, no alloy SDS read
      lead: PubChem records cover elemental chromium, molybdenum and manganese. No safety data sheet for the 4130 bar was read in this run.
      points:
        - label: Chromium
          line: PubChem lists elemental chromium as Danger, with H317, H319 and H334 among its reported codes. 50 percent of reports say it does not meet GHS hazard criteria.
        - label: Molybdenum
          line: PubChem lists elemental molybdenum as Danger, with H361 (suspected of damaging fertility or the unborn child) and H228 (flammable solid) among its codes.
        - label: Manganese
          line: PubChem lists elemental manganese as Danger, with H360 and H372 among its codes.
    - title: In service
      level: 2
      verdict: Hydrogen and salt are the watch points
      lead: These come from laboratory tests, not from field incidents.
      points:
        - label: Hydrogen gas
          line: At 21 to 69 MPa hydrogen and 286 K, the threshold stress intensity of the 635 MPa yield strength level fell from 88 to 32 MPa√m (Sandia).
        - label: Salt solution
          line: In aerated NaCl and CaCl2 solution, every corrosion-fatigue specimen failed in under 150,000 cycles (Georgia Tech thesis).
    - title: Welding
      level: 2
      verdict: Preheat and stress relief are needed
      lead: Welding 4130 is workable, but it is prone to hydrogen cracking if preheat and heat treatment are skipped.
      points:
        - label: Hydrogen cracking
          line: Material Welding says 4130 is particularly prone to hydrogen cracking, which fully baked consumables and slower cooling reduce.
        - label: Preheat
          line: Preheat to about 200 to 300 C (400 to 570 F), with the upper end for sections thicker than 25 mm.
  why: AISI 4130 (UNS G41300) is a low-alloy chromium-molybdenum steel that aircraft and motorsport builders, oil and gas makers and NASA's heritage list use. Aircraft Materials cites its weldability and ease of fabrication, and Titanium Industries cites good strength, toughness and weldability. Its numbers depend on the heat treatment, so every value in this profile carries its own condition. Hydrogen gas and salt solutions are its weak points, both in laboratory tests.
  uses:
    - where: Rocket motors and launch vehicles
      line: NASA's heritage list for launch vehicles names 4130 as a solid rocket booster case material, alongside D6AC and maraging steel.
    - where: Aircraft tube, sheet and bar
      line: Aircraft Materials lists 4130 tube to AMS 6371, bar to AMS 6346 and sheet to AMS 6350 for military and commercial aircraft.
    - where: Oil and gas parts
      line: Quenched and tempered 4130 round bar goes into oil and gas drilling and production parts, such as wellhead and Christmas tree parts (Material Welding).
  can_do:
    - label: Strength
      line: Quenched and tempered with a temper at about 635 C, the Sandia heat treatment gives 635 MPa yield strength and 820 MPa tensile strength, with 67 percent reduction of area.
    - label: Normalised
      line: Normalised at 870 C, the MatWeb record gives 670 MPa tensile strength, 435 MPa yield strength, 25.5 percent elongation in 50 mm and 197 HB.
    - label: Hardness
      line: Round bar usually supplied quenched and tempered sits at 18 to 22 HRC (Material Welding).
    - label: Stiffness
      line: The modulus of elasticity is 205 GPa, marked typical for steel (MatWeb).
    - label: Weldability
      line: Material Welding says it welds well when preheat, interpass temperature and post-weld heat treatment are controlled; Titanium Industries cites good weldability.
  compare: No source read in this run compares AISI 4130 with AISI 4140 head to head. The Sandia report prints both grades in the same tables, but their heat treatments differ, so the 4130 and 4140 rows cannot be read as a like-for-like comparison, and no 4140 value is used in this file. To compare the two, first match the heat-treatment condition, then compare the yield strength, elastic modulus and density rows below.
  compare_rows:
    - label: Strength (yield)
      benchmark: yield_strength
    - label: Stiffness
      benchmark: elastic_modulus
    - label: Density
      benchmark: density
  handling:
    - Quote the heat-treatment condition with every strength value, because the normalised, annealed, quenched-and-tempered and hydrogen-tested rows differ.
    - Preheat before welding to about 200 to 300 C (400 to 570 F), with the upper end for sections thicker than 25 mm, and use fully baked consumables.
    - Stress relieve parts thicker than 3 mm (0.120 in) at about 600 C, and keep the temperature below the tempering temperature.
    - 'In hydrogen service, do not assume a high-strength 4130 is safe: the threshold fell from 88 to 32 MPa√m as pressure rose from 21 to 69 MPa in one study.'
    - Take the safety data sheet for the specific bar before cutting, grinding or welding; no 4130 SDS was read here.
  good_for:
    - Aircraft and motorsport tube, sheet and bar, where weldability and strength after heat treatment matter (Aircraft Materials).
    - Oil and gas wellhead and Christmas tree parts in quenched and tempered round bar (Material Welding).
    - Forged valve bodies, pumps and machine tool components (Titanium Industries, Aircraft Materials).
  watch_out:
    - 'Hydrogen gas: the threshold stress intensity of 4130 fell from 88 to 32 MPa√m between 21 and 69 MPa hydrogen (Sandia).'
    - 'Salt solutions: every corrosion-fatigue specimen tested in aerated NaCl and CaCl2 solution failed in under 150,000 cycles (Georgia Tech thesis).'
    - Welding without preheat, post-weld heat treatment or baked consumables risks hydrogen cracking (Material Welding).
  verdict: AISI 4130 is a weldable, heat-treatable chromium-molybdenum steel for aircraft tube and sheet, oil and gas parts and machine parts. Its strength depends on heat treatment, so quote the condition with every value. Hydrogen and salt solutions are the watch points, and the hydrogen data come from laboratory tests, not field service.