Super-austenitic stainless steel 904L 904L (UNS N08904, EN 1.4539)

spore: profile
id: stainless-904l
spore_version: 0.2
family: stainless-austenitic
name: Super-austenitic stainless steel 904L
abbreviation: 904L (UNS N08904, EN 1.4539)
role: corrosion-resistant austenitic alloy
category: metals
type: steels-and-stainless
summary: |
  904L (UNS N08904, EN 1.4539, sold by Outokumpu as Ultra 904L) is a super-austenitic stainless steel with about 20 percent chromium, 24 percent nickel, 4.3 percent molybdenum and 1.4 percent copper. Outokumpu's typical PRE is 34. Its minimum proof strength is 220 MPa for plate, sheet and strip to ASTM, and 240 MPa for cold-rolled strip to EN 10088-2. It is annealed at 1060 to 1140 °C and quenched. It is used for sulfuric and phosphoric acid plant, utility scrubbers, seawater heat exchangers, pulp and paper bleaching and pickling equipment. No spacecraft use is recorded in the sources read.
best_for: Sulfuric and phosphoric acid plant, seawater condensers and heat exchangers, and pulp bleaching, in annealed sheet, plate, strip and tube, where 316L or 317L would corrode
weakest_at: Halide-containing acids and boiling magnesium or lithium chloride, where ATI's U-bend test cracked the alloy, and crevices in chloride water (ATI G-48 onset at 18 °C)
identity:
  formula: Fe balance; Outokumpu typical 19.8 Cr, 24.2 Ni, 4.3 Mo, 1.4 Cu, 0.01 C (wt%); ASTM ranges 19 to 23 Cr, 23 to 28 Ni, 4 to 5 Mo, 1 to 2 Cu, max 0.02 C, 2 Mn, 1 Si (wt%)
  source: outokumpu-ultra
  where: Table 1 (chemical composition, typical values), row Ultra 904L. The ASTM ranges come from the Sandmeyer specification sheet, Chemical Analysis table.
  designations:
    - system: UNS
      code: N08904
      source: outokumpu-ultra
      where: Table 1, UNS column, row Ultra 904L
    - system: EN
      code: '1.4539'
      source: outokumpu-ultra
      where: Table 1, EN column, row Ultra 904L
    - system: EN name
      code: X1NiCrMoCu25-20-5
      source: metalcor-1-4539
      where: Designation table, EN Designation row
    - system: AISI
      code: 904L
      source: metalcor-1-4539
      where: Designation table, AISI/SAE row (printed as 904 L)
    - system: ASTM
      code: A240
      note: plate, sheet and strip
      source: outokumpu-ultra
      where: Table 11, ASTM A240 section, row Ultra 904L (EN 1.4539, UNS N08904)
    - system: ASTM
      code: B625
      note: plate, sheet and strip
      source: ati-904l
      where: Mechanical properties, ASTM and ASME coverage table, Plate, Sheet and Strip row
    - system: ASTM
      code: B677
      note: seamless pipe and tube
      source: ati-904l
      where: Mechanical properties, ASTM and ASME coverage table, Seamless Pipe and Tube row
    - system: BS
      code: 904S13
      source: spacemat-904l
      where: Equivalent Designations line, BS904S13
    - system: JIS
      code: SUS 904L
      source: wiki-sae904l
      where: Infobox, other names
    - system: Trade name
      code: Ultra 904L
      source: outokumpu-ultra
      where: Table 1 and Table 2, Outokumpu name column
    - system: Trade name
      code: ATI 904L
      source: ati-904l
      where: Title block of the ATI technical data sheet
tags:
  environments: []
  stresses: []
  applications:
    - structures
properties:
  - benchmark: density
    label: Density, 904L (ASTM datasheet)
    value: 7.95
    unit: g/cm3
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: not stated
    method: Value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Physical Properties, Density (7.95 g/cm3)
  - benchmark: density
    label: Density, Ultra 904L (EN 10088-1 values)
    value: 8
    unit: kg/dm3
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 20 °C
      basis: EN 10088-1 table, rounded to one decimal
    method: Value printed in the physical properties table of the Outokumpu Ultra range datasheet
    status: ground
    source: outokumpu-ultra
    where: Table 13, Physical properties, Density column, row Ultra 904L
  - benchmark: elastic_modulus
    label: Modulus of elasticity, Ultra 904L at 20 °C
    value: 195
    unit: GPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 20 °C
    method: Value printed in the physical properties table of the Outokumpu Ultra range datasheet
    status: ground
    source: outokumpu-ultra
    where: Table 13, Physical properties, Modulus of elasticity at 20 °C column, row Ultra 904L
  - benchmark: elastic_modulus
    label: Modulus of elasticity, alloy 904L
    value: 190
    unit: GPa
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: not stated
    method: Value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Physical Properties, Modulus of Elasticity (190 GPa)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Ultra 904L at 20 °C
    value: 12
    unit: W/(m·K)
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 20 °C
    method: Value printed in the physical properties table of the Outokumpu Ultra range datasheet
    status: ground
    source: outokumpu-ultra
    where: Table 13, Physical properties, Thermal conductivity at 20 °C column, row Ultra 904L
  - benchmark: thermal_conductivity
    label: Thermal conductivity, alloy 904L at 100 °C
    value: 12.9
    unit: W/(m·K)
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: 100 °C
      unit_in_source: 6.8 BTU/ft h °F
    method: Value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Physical Properties, Thermal Conductivity 212°F (100°C) row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, alloy 904L at 200 °C
    value: 15.2
    unit: W/(m·K)
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: 200 °C
      unit_in_source: 8.8 BTU/ft h °F
    method: Typical value printed in a manufacturer data sheet (ATI, 2012 edition)
    status: ground
    source: ati-904l
    where: Physical Properties, Thermal Conductivity table, 392°F (200°C) row
  - benchmark: specific_heat
    label: Specific heat capacity, Ultra 904L at 20 °C
    value: 450
    unit: J/(kg·K)
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 20 °C
    method: Value printed in the physical properties table of the Outokumpu Ultra range datasheet
    status: ground
    source: outokumpu-ultra
    where: Table 13, Physical properties, Thermal capacity at 20 °C column, row Ultra 904L
  - benchmark: cte
    label: Mean coefficient of thermal expansion, Ultra 904L, 20 to 100 °C
    value: 15.8
    unit: ppm/K
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 20 to 100 °C
    method: Value printed in the physical properties table of the Outokumpu Ultra range datasheet (10-6/K)
    status: ground
    source: outokumpu-ultra
    where: Table 13, Physical properties, Coefficient of thermal expansion 20 to 100 °C column, row Ultra 904L
  - benchmark: cte
    label: Mean coefficient of thermal expansion, alloy 904L, 20 to 100 °C
    value: 15.3
    unit: ppm/K
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: 20 to 100 °C
      unit_in_source: 8.5 x 10-6/°F (68 to 212 °F)
    method: Value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Mean Coefficient of Thermal Expansion table, 20 to 100 °C row
  - benchmark: cte
    label: Mean coefficient of thermal expansion, alloy 904L, 20 to 400 °C
    value: 16.5
    unit: ppm/K
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: 20 to 400 °C
      unit_in_source: 9.2 x 10-6/°F (68 to 750 °F)
    method: Typical value printed in a manufacturer data sheet (ATI, 2012 edition)
    status: ground
    source: ati-904l
    where: Average Coefficient of Thermal Expansion table, 20-400°C row
  - benchmark: electrical_resistivity
    label: Electrical resistivity, alloy 904L at 20 °C
    value: 95.2
    unit: µΩ·cm
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temperature: 20 °C
      unit_in_source: 95.2 microhm-cm at 20°C
    method: Value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Electrical Resistivity entry, 95.2 Microhm-cm at 20°C
  - benchmark: melting_point
    label: Melting range, alloy 904L
    value: 1300
    value_high: 1390
    bound: range
    unit: °C
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      unit_in_source: 2372 to 2534 °F
    method: Melting range printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Melting Range entry, 1300 to 1390 °C
  - benchmark: yield_strength
    label: Proof strength Rp0.2, cold-rolled, minimum (EN 10088-2)
    value: 240
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      form: cold-rolled coil and sheet
      temperature: 20 °C
      basis: minimum, EN 10088-2
    method: Minimum value printed in the mechanical properties table, EN 10088-2 basis
    status: ground
    source: outokumpu-ultra
    where: Table 10, Mechanical properties at 20 °C, Min. yield strength Rp0.2 column, row Ultra 904L, Cold rolled
  - benchmark: yield_strength
    label: Proof strength Rp0.2, hot-rolled and plate, minimum (EN 10088-2)
    value: 220
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      form: hot-rolled coil and sheet, and plate
      temperature: 20 °C
      basis: minimum, EN 10088-2
    method: Minimum value printed in the mechanical properties table, EN 10088-2 basis
    status: ground
    source: outokumpu-ultra
    where: Table 10, Mechanical properties at 20 °C, Min. yield strength Rp0.2 column, rows Ultra 904L Hot rolled and Plate
  - benchmark: yield_strength
    label: Yield strength Rp0.2, annealed plate, sheet and strip, minimum (ASTM B625)
    value: 220
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      form: plate, sheet and strip, annealed
      temperature: 20 °C
      basis: minimum, ASTM and ASME specified properties
      unit_in_source: 31,000 psi
    method: Minimum value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Mechanical properties table, Yield Strength 0.2% Offset, 31,000 psi (220 MPa) row
  - benchmark: yield_strength
    label: Yield strength Rp0.2, annealed, typical (ATI)
    value: 270
    unit: MPa
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temper: annealed
      temperature: 20 °C
      basis: typical, not a minimum
      unit_in_source: 39,500 psi
    method: Typical value printed in a manufacturer data sheet (ATI, 2012 edition)
    status: ground
    source: ati-904l
    where: Mechanical Properties, Typical (and minimum) table, Yield Strength row, typical column
  - benchmark: yield_strength
    label: Proof strength Rp0.2 at 100 °C, minimum (EN 10088-2)
    value: 205
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 100 °C
      basis: minimum, EN 10088-2
    method: Minimum value printed in the elevated temperature table
    status: ground
    source: outokumpu-ultra
    where: Table 12, Mechanical properties at elevated temperatures, Proof strength Rp0.2 row, 100 °C column
  - benchmark: yield_strength
    label: Proof strength Rp0.2 at 300 °C, minimum (EN 10088-2)
    value: 145
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 300 °C
      basis: minimum, EN 10088-2
    method: Minimum value printed in the elevated temperature table
    status: ground
    source: outokumpu-ultra
    where: Table 12, Mechanical properties at elevated temperatures, Proof strength Rp0.2 row, 300 °C column
  - benchmark: yield_strength
    label: Proof strength Rp0.2 at 500 °C, minimum (EN 10088-2)
    value: 110
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      temperature: 500 °C
      basis: minimum, EN 10088-2
    method: Minimum value printed in the elevated temperature table
    status: ground
    source: outokumpu-ultra
    where: Table 12, Mechanical properties at elevated temperatures, Proof strength Rp0.2 row, 500 °C column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength Rm, cold-rolled (EN 10088-2)
    value: 530
    value_high: 730
    bound: range
    unit: MPa
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      form: cold-rolled coil and sheet
      temperature: 20 °C
      basis: range printed as minimum-to-maximum, EN 10088-2
    method: Range printed in the mechanical properties table, EN 10088-2 basis
    status: ground
    source: outokumpu-ultra
    where: Table 10, Mechanical properties at 20 °C, Tensile strength Rm column, row Ultra 904L, Cold rolled
  - benchmark: ultimate_tensile_strength
    label: Tensile strength Rm, annealed, minimum (ASTM B625)
    value: 490
    bound: lower
    unit: MPa
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      form: plate, sheet and strip, annealed
      temperature: 20 °C
      basis: minimum, ASTM and ASME specified properties
      unit_in_source: 71,000 psi
    method: Minimum value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Mechanical properties table, Ultimate Tensile Strength row, 71,000 psi (490 MPa)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength Rm, annealed, typical (ATI)
    value: 605
    unit: MPa
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temper: annealed
      temperature: 20 °C
      basis: typical, not a minimum
      unit_in_source: 88,000 psi
    method: Typical value printed in a manufacturer data sheet (ATI, 2012 edition)
    status: ground
    source: ati-904l
    where: Mechanical Properties, Typical (and minimum) table, Tensile Strength row, typical column
  - benchmark: elongation
    label: Elongation A, cold-rolled and hot-rolled, minimum (EN 10088-2)
    value: 35
    bound: lower
    unit: '%'
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      form: cold-rolled and hot-rolled
      temperature: 20 °C
      gauge: A, L0 = 5.65 times the square root of S0 (thickness 3 mm or more)
      basis: minimum, EN 10088-2
    method: Minimum value printed in the mechanical properties table
    status: ground
    source: outokumpu-ultra
    where: Table 10, Mechanical properties at 20 °C, Min. elongation A column, row Ultra 904L, Cold rolled and Hot rolled
  - benchmark: elongation
    label: Elongation in 2 in, annealed, minimum (ASTM B625)
    value: 36
    bound: lower
    unit: '%'
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      form: plate, sheet and strip, annealed
      temperature: 20 °C
      gauge: 2 in
      basis: minimum, ASTM and ASME specified properties
    method: Minimum value printed in a specification sheet for alloy 904L
    status: ground
    source: sandmeyer-904l
    where: Mechanical properties table, Elongation in 2 in. row, 36 % minimum
  - benchmark: hardness
    label: Hardness HB 30, maximum at 20 °C (EN 1.4539)
    value: 230
    bound: upper
    unit: HB
    scope: material
    conditions:
      grade: 1.4539 (EN)
      temperature: 20 °C
      basis: maximum
    method: Maximum value printed in the mechanical properties table of the Metalcor 1.4539 datasheet
    status: ground
    source: metalcor-1-4539
    where: Mechanical Properties at 20 °C table, Hardness HB 30 row
  - benchmark: hardness
    label: Hardness Brinell, annealed, typical (ATI)
    value: 150
    unit: HB
    scope: material
    conditions:
      grade: 904L (UNS N08904)
      temper: annealed
      temperature: 20 °C
      basis: typical, shown for information only
    method: Typical value printed in a manufacturer data sheet (ATI, 2012 edition)
    status: ground
    source: ati-904l
    where: Mechanical Properties, Typical (and minimum) table, Hardness (Brinell) row
  - benchmark: pren
    label: Pitting resistance equivalent PRE, Ultra 904L (Cr + 3.3 Mo + 16 N)
    value: 34
    unit: '-'
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      basis: Outokumpu typical composition, PRE = %Cr + 3.3 x %Mo + 16 x %N
    method: Value printed in the PRE table of the Outokumpu Ultra range datasheet
    status: ground
    source: outokumpu-ultra
    where: Table 7, PRE values, row Ultra 904L (Table 1 also prints 34)
  - benchmark: critical_crevice_temperature
    label: Critical crevice corrosion onset temperature, 10% ferric chloride, ASTM G-48
    value: 18
    unit: °C
    scope: material
    conditions:
      grade: 904L (ATI)
      test: 10% ferric chloride, ASTM G-48 (artificial crevices)
      unit_in_source: 65 °F
    method: Onset temperature printed in a manufacturer data sheet (ATI, 2012 edition)
    status: ground
    source: ati-904l
    where: Pitting Corrosion section, G-48 onset table, row ATI 904L
  - benchmark: max_service_temp
    label: Upper temperature for pressure-vessel approval
    value: 400
    bound: upper
    unit: °C
    scope: material
    conditions:
      grade: Ultra 904L (EN 1.4539)
      basis: pressure vessel approval range is -196 to +400 °C; a design code limit, not a creep or oxidation limit
    method: Value printed in the typical temperatures table of the Outokumpu Ultra range datasheet
    status: ground
    source: outokumpu-ultra
    where: Table 8, Typical temperatures, Pressure vessel approval column, row Ultra 904L
corrosion:
  - environment: Boiling sulfuric acid, 10 percent
    headline: In boiling 10 percent sulfuric acid, 904L corrodes at 101 mpy (2.57 mm/a), against 636 mpy (16.2 mm/a) for ATI 316.
    effect: ATI's laboratory table of boiling solutions gives typical rates. 904L is also rated by Sandmeyer as fully resistant to dilute sulfuric acid across the 0 to 100 percent range at up to 35 °C.
    rating: moderate
    conditions:
      solution: 10% H2SO4 (boiling)
      comparison: ATI 316 at 636 mpy
      basis: typical, laboratory boiling test
    source: ati-904l
    where: Boiling Solution table, row 10% Sulfuric Acid
  - environment: Ambient and wet process phosphoric acid
    headline: In wet process phosphoric acid at 60 °C, 904L corrodes at 1.2 mm/year, against more than 5 mm/year for 316L.
    effect: Outokumpu's wet-process test uses a 54 percent P2O5 acid with impurities. The table shows that 904L is much lower than standard 316L, though Ultra 254 SMO, at 0.05 mm/year, is lower still.
    rating: low
    conditions:
      solution: wet process phosphoric acid, 54% P2O5 with impurities
      temperature: 60 °C
    source: outokumpu-ultra
    where: Table 4, Uniform corrosion in wet process phosphoric acid at 60 °C, row Ultra 904L
  - environment: Pickling acid, nitric and hydrofluoric
    headline: In a pickling acid at 25 °C, 904L corrodes at 0.47 mm/year, against more than 6 mm/year for 316L.
    effect: Sandmeyer's pickling table gives the same 0.47 mm/year for 904L and more than 6 mm/year for 316L in the same acid.
    rating: low
    conditions:
      solution: 20% HNO3 + 4% HF
      temperature: 25 °C
    source: outokumpu-ultra
    where: Table 5, Uniform corrosion in pickling acid at 25 °C, row Ultra 904L
  - environment: Fatty acid column for tall oil distillation
    headline: In a tall oil fatty acid column at 235 °C, 904L corrodes at 0.06 mm/year, against 0.88 mm/year for 316L.
    effect: Sandmeyer gives the same kind of result at 253 °C, with 0.06 mm/year for 904L and 0.29 for 317LMN. Outokumpu says the nickel content sets resistance in hot concentrated caustic.
    rating: low
    conditions:
      temperature: 235 °C
      comparison: Supra 316L/4404 at 0.88 mm/year
    source: outokumpu-ultra
    where: Table 6, Corrosion rates in a fatty acid column, row Ultra 904L
  - environment: Chloride pitting and crevices in aerated seawater
    headline: The alloy is not totally resistant to aerated seawater, but it resists pitting and crevices better than 316.
    effect: ATI says 904L suits tubesheets in seawater heat exchangers and pulp bleach plant equipment where some attack can be tolerated. Outokumpu says the risk of crevice corrosion in non-chlorinated seawater is considerably lower, and that chlorination raises the corrosion potential of the steel.
    rating: moderate
    conditions:
      medium: aerated seawater
      comparison: 316 has an onset of 27 °F (-3 °C) in the G-48 test
    source: ati-904l
    where: Pitting Corrosion section, first and second paragraphs
  - environment: Chloride stress corrosion cracking, boiling chloride solutions
    headline: U-bend specimens cracked in boiling 42 percent magnesium chloride and 33 percent lithium chloride in 1000 hours, but not in 26 percent sodium chloride.
    effect: ATI calls 904L much better than Type 304 for chloride cracking because of its 25 percent nickel and 4.5 percent molybdenum, but says it is not completely resistant to the boiling magnesium and lithium chloride tests.
    rating: moderate
    conditions:
      test: U-bend, boiling solutions, 1000 hours
      solutions: 42% MgCl2, 33% LiCl, 26% NaCl
    source: ati-904l
    where: Chloride Stress Corrosion Cracking section, Performance Using U-Bend Samples table
  - environment: Intergranular attack after welding
    headline: In the ASTM A262 practice B ferric sulfate and sulfuric acid test, 904L corrodes at 14.2 mpy, against 35.5 mpy for 316.
    effect: Low carbon keeps 904L resistant to intergranular attack in the welded condition. Sandmeyer says segregation after welding is less evident in 904L than in 316L or 317LMN.
    rating: low
    conditions:
      test: ASTM A262 practice B, ferric sulfate-sulfuric acid
      comparison: ATI 316 at 35.5 mpy
    source: ati-904l
    where: Intergranular Corrosion Resistance table, Ferric Sulfate-Sulfuric Acid row
  - environment: Halide-containing acids
    headline: Acids with halide ions can be very aggressive, and the corrosion resistance of 904L may be insufficient.
    effect: Sandmeyer names 317L, 317LMN and 904L together as possibly insufficient in such acids. Outokumpu says all stainless steels are sensitive to hydrofluoric, hydrochloric and fluosilicic acids.
    rating: moderate
    conditions:
      acids: hydrofluoric, hydrochloric, fluosilicic, and other halide-containing acids
    source: sandmeyer-904l
    where: Corrosion Resistance section, first paragraph
risks:
  hazards:
    - text: PubChem's GHS record for elemental nickel lists H317, H351 and H372 as statements without a percentage. These describe the element, not the alloy.
      ghs:
        - H317
        - H351
        - H372
      source: pubchem-nickel
      where: GHS Classification, Hazard Statements list (CID 935)
    - text: PubChem's GHS record for elemental chromium lists H317, H334 and H335 as statements without a percentage. These describe the element, not the alloy.
      ghs:
        - H317
        - H334
        - H335
      source: pubchem-chromium
      where: GHS Classification, Hazard Statements list (CID 23976)
    - text: PubChem's GHS record for elemental molybdenum lists H315, H319 and H335 as statements without a percentage. These describe the element, not the alloy.
      ghs:
        - H315
        - H319
        - H335
      source: pubchem-molybdenum
      where: GHS Classification, Hazard Statements list (CID 23932)
    - text: PubChem's GHS record for elemental copper lists H400 and H410 as statements without a percentage. These describe the element, not the alloy.
      ghs:
        - H400
        - H410
      source: pubchem-copper
      where: GHS Classification, Hazard Statements list (CID 23978)
  failure_risks:
    - mode: Chloride stress corrosion cracking in boiling chloride
      trigger: Boiling magnesium or lithium chloride, or hot chloride brine under tensile stress
      consequence: ATI's U-bend test cracked 904L in boiling 42 percent MgCl2 and 33 percent LiCl within 1000 hours, so the alloy is not immune in these tests.
      severity: moderate
      source: ati-904l
      where: Chloride Stress Corrosion Cracking section, U-bend table
    - mode: Crevice and pitting attack in chloride water
      trigger: Crevices in chloride water above about 18 °C under the G-48 test conditions
      consequence: ATI gives the G-48 onset as 18 °C for 904L against 45 °C for AL-6XN. Crevices are a design limit in warm chloride water.
      severity: moderate
      source: ati-904l
      where: Pitting Corrosion section, G-48 onset table
    - mode: Attack by halide-containing acids
      trigger: Acids containing chloride or fluoride ions
      consequence: Sandmeyer says 904L may not be resistant enough in these acids, which can be very aggressive.
      severity: moderate
      source: sandmeyer-904l
      where: Corrosion Resistance section, first paragraph
    - mode: Higher forming loads and fast work hardening
      trigger: Cold forming, bending or pressing sheet
      consequence: 904L is somewhat stronger than 304 and 316, so it needs higher loads to deform, and cold work hardens it quickly.
      severity: low
      source: ati-904l
      where: Formability section
  side_effects: []
  handling:
    - text: Solution anneal at 1060 to 1140 °C and quench (Outokumpu Table 8; Sandmeyer heat treatment).
      source: outokumpu-ultra
      where: Table 8, Solution annealing column, row Ultra 904L
    - text: Hot working is done at 1150 to 850 °C (Outokumpu Table 8). Sandmeyer says hot forming that ends above 1100 °C, with the whole workpiece quenched directly, may be used without a further heat treatment; otherwise a solution anneal is needed.
      source: sandmeyer-904l
      where: Hot Forming section
    - text: Weld with low heat input. Outokumpu says the Ultra grades are more sensitive to hot cracking than conventional austenitic steels.
      source: outokumpu-ultra
      where: Welding section
    - text: Use a 20 25 5 Cu L filler. The covered electrode is 20 25 5 Cu L (ISO 3581 and 14172) and the wire is 20 25 5 Cu L (ISO 14343 and 18274). Sandmeyer gives 20 25 CuL as its filler.
      source: outokumpu-ultra
      where: Table 9, Welding consumables, row Ultra 904L
    - text: Sandmeyer says a filler of the same composition as the base metal is normal, and that welds in 904L segregate less than in 316L or 317LMN.
      source: sandmeyer-904l
      where: Welding section
    - text: Machining is harder than for 410 and 304 because of work hardening.
      source: sandmeyer-904l
      where: Machining section
    - text: Outokumpu says a post-fabrication treatment is often needed after welding to restore the surface and corrosion resistance, by brushing, blasting, grinding or pickling.
      source: outokumpu-ultra
      where: Welding section, post-fabrication treatment paragraph
  mitigations:
    - text: For welds in corrosive media, use a more highly alloyed austenitic filler, which ATI says gives the best weld corrosion properties.
      source: ati-904l
      where: Weldability section
    - text: Specify solution annealing and quenching after heavy hot work, so the material returns to its corrosion-resistant condition.
      source: outokumpu-ultra
      where: Table 8, Solution annealing column
    - text: Design out crevices in chloride water. ATI's G-48 onset of 18 °C shows that crevices can start attack at warm temperatures.
      source: ati-904l
      where: Pitting Corrosion section, G-48 table
uses:
  - application: structures
    device: Seawater condensers, heat exchangers and piping
    example: Sandmeyer lists condensers, heat exchangers and piping systems for seawater and brackish water. ATI lists tubesheets in seawater heat exchangers.
    source: sandmeyer-904l
    where: Applications list, Seawater and Brackish Water item
  - application: structures
    device: Utility scrubbers and air pollution control equipment
    example: Sandmeyer lists scrubbers for coal-fired power plants, and ATI lists utility scrubbers among its service environments.
    source: sandmeyer-904l
    where: Applications list, Air Pollution Control item
  - application: structures
    device: Sulfuric and phosphoric acid process equipment
    example: Outokumpu lists pipes, heat exchangers, tanks and reactor vessels for chemical and petrochemical industry, plus sulfuric acid handling, flanges and valves.
    source: outokumpu-ultra
    where: Table 2, Key Ultra grades, Ultra 904L row, Typical applications column
  - application: structures
    device: Pulp and paper bleach plant equipment
    example: ATI says 904L suits pulp and paper bleach plant equipment where resistance above that of 316 is wanted, though some attack can be tolerated.
    source: ati-904l
    where: Pitting Corrosion section
  - application: structures
    device: Pickling equipment using sulfuric acid
    example: Sandmeyer lists pickling equipment that uses sulfuric acid among its applications.
    source: sandmeyer-904l
    where: Applications list, Metallurgical Processing item
  - application: structures
    device: Offshore process equipment for oil and gas production
    example: Sandmeyer lists offshore process equipment in its oil and gas production application.
    source: sandmeyer-904l
    where: Applications list, Oil and Gas Production item
  - application: structures
    device: Pharmaceutical process equipment
    example: Sandmeyer lists process equipment for the pharmaceutical industry.
    source: sandmeyer-904l
    where: Applications list, Pharmaceutical Industry item
supply:
  - subject: Nickel
    abundance: World mine production 3,900,000 tons of nickel content in 2025 (estimated), with reserves above 140,000,000 tons (USGS 2026).
    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: New Caledonia
        share_percent: 3.6
        year: 2025
      - country: Canada
        share_percent: 3.6
        year: 2025
      - country: China
        share_percent: 3.1
        year: 2025
    critical_lists: []
    recycling: Nickel recovered from scrap was about 60 percent of US apparent consumption in 2025, mostly from stainless-steel scrap.
    substitutes:
      - Low-nickel, duplex or ultrahigh-chromium stainless steels have been substituted for austenitic grades in construction (USGS 2026).
      - Titanium alloys can substitute for nickel or nickel-base alloys in corrosive environments (USGS 2026).
    source: usgs-nickel-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated from printed tonnages); Salient Statistics; Recycling; Substitutes
  - subject: Chromium
    abundance: World mine production 51,000 thousand metric tons of ore, gross weight, in 2025 (estimated). World resources are greater than 12 billion tons of shipping-grade chromite.
    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: []
    recycling: Recycled chromium in 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 (USGS 2026).
    source: usgs-chromium-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated from printed tonnages); World Resources; Salient Statistics; Import Sources; Substitutes
  - subject: Molybdenum
    abundance: World mine production 260,000 metric tons of molybdenum content in 2025 (estimated). China, Chile, the United States, Peru and Mexico produce 90 percent of the total.
    producers:
      - country: China
        share_percent: 37.3
        year: 2025
      - country: Chile
        share_percent: 16.2
        year: 2025
      - country: United States
        share_percent: 15.4
        year: 2025
      - country: Peru
        share_percent: 15
        year: 2025
      - country: Mexico
        share_percent: 6.5
        year: 2025
    critical_lists: []
    recycling: Molybdenum is recycled from catalysts, ferrous scrap and superalloy scrap. Revert and new scrap are reused in the steel industry.
    substitutes:
      - There is little substitution for molybdenum in steels and cast irons (USGS 2026).
    source: usgs-molybdenum-2026
    where: World Mine Production and Reserves table, 2025e column (shares calculated from printed tonnages); Events, Trends, and Issues; Recycling; Substitutes
  - subject: Copper
    abundance: World mine production 23,000 thousand metric tons of copper content in 2025 (estimated). The US added copper to its 2025 list of critical minerals.
    producers:
      - country: Chile
        share_percent: 23
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 13.9
        year: 2025
      - country: Peru
        share_percent: 11.7
        year: 2025
      - country: China
        share_percent: 7.8
        year: 2025
      - country: United States
        share_percent: 4.3
        year: 2025
    critical_lists:
      - list: U.S. Final 2025 List of Critical Minerals (copper added in 2025)
        listed: true
    recycling: Old scrap gave an estimated 160,000 tons of copper in 2025, and copper recovered from scrap was about 30 percent of US copper supply.
    substitutes:
      - Aluminum substitutes for copper in several electrical and cooling uses (USGS 2026).
    source: usgs-copper-2026
    where: World Mine and Refinery Production table, 2025e column (shares calculated from printed tonnages); Critical Minerals paragraph; Recycling; Substitutes
media: []
documents:
  - title: 'Outokumpu: Ultra range datasheet (Ultra 904L, EN 1.4539, UNS N08904)'
    type: datasheet
    url: https://www.outokumpu.com/-/media/files/products/ultra/outokumpu_ultra_range_datasheet.pdf?revision=5e1844a6-f25c-49d4-b15b-3d84c47c9c31&modified=20250120090629
    year: 2025
  - title: 'ATI: ATI 904L technical data sheet, version 1 (2012)'
    type: datasheet
    url: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/superaustenitic/ati_904l_tds_en_v1.pdf
    year: 2012
  - title: 'Sandmeyer Steel: Alloy 904L specification sheet (rev 02/2023)'
    type: datasheet
    url: https://www.sandmeyersteel.com/wp-content/uploads/Alloy904L-SpecSheet.pdf
    year: 2023
  - title: 'Metalcor: 1.4539 (AISI 904 L / N08904) datasheet'
    type: datasheet
    url: http://www.metalcor.de/en/datenblatt/32/
  - title: 'SpaceMat: AISI 904L entry'
    type: database
    url: https://www.spacematdb.com/spacemat/datasearch.php?name=AISI+904L
  - 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: Copper'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.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
    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
    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
    year: 2026
  - title: 'PubChem: Copper (CID 23978), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23978/JSON
    year: 2026
gaps:
  - No spacecraft, rocket or satellite use is recorded. SpaceMat rates the space experience of AISI 904L as "Limited" and names no flight, mission, outgassing or atomic-oxygen data, so tags.environments is empty and no space use is listed.
  - Mechanical values differ by standard and product form. Outokumpu gives EN 10088-2 minima, the Sandmeyer sheet gives ASTM B625 minima, and the ATI values are typical (2012 edition). Each property states its basis in conditions.
  - The EN 1.4539 composition in the Metalcor datasheet has narrower ranges than the ASTM ranges (19 to 21 Cr, 24 to 26 Ni, 4 to 5 Mo, 1.2 to 2.0 Cu, 0.02 max C). Only the ASTM ranges are quoted in identity.formula.
  - The SpaceMat page prints the EN name as X1NiCrMoCuN25-20-5. Only the Metalcor form, X1NiCrMoCu25-20-5, is listed as a designation.
  - Outokumpu Figures 8, 9 and 11 (critical pitting temperature, critical crevice temperature and drop-evaporation threshold) are graphs with no printed values, so no values are taken from them.
  - Impact energy, fatigue strength and Poisson's ratio have no printed numbers in the sources used. ATI describes the impact behaviour only as excellent at sub-zero temperatures.
  - The ATI sheet is the 2012 version. Its corrosion and physical values are typical, not minimum or maximum values.
  - A tube supplier's page (Finetubes) gives a maximum service temperature of 450 °C. It is not used, because no basis is printed, and Outokumpu's pressure-vessel range is 400 °C.
  - Supply shares are calculated from the 2025 estimated mine-production tonnages in each USGS table. They are mine output only, not refining or smelting.
  - The US critical-minerals status is recorded only for copper, which the USGS copper summary says was added in the 2025 list. The 2026 nickel, chromium and molybdenum summaries do not state their status, so their critical_lists are empty.
  - Hazard statements are PubChem element records for nickel, chromium, molybdenum and copper, taken from the statements that appear without a percentage. No safety data sheet for the alloy was checked.
  - Critical pitting temperature and the ASTM G-48 method for Ultra 904L have no printed value in the Outokumpu datasheet, so only the ATI G-48 onset is recorded.
sources:
  outokumpu-ultra:
    title: 'Outokumpu: Ultra range datasheet (Ultra 904L, EN 1.4539, UNS N08904)'
    id: Outokumpu Ultra range datasheet, outokumpu.com/ultra
    url: https://www.outokumpu.com/-/media/files/products/ultra/outokumpu_ultra_range_datasheet.pdf?revision=5e1844a6-f25c-49d4-b15b-3d84c47c9c31&modified=20250120090629
    kind: datasheet
    year: 2025
    license: cited, not reproduced
  ati-904l:
    title: 'ATI: ATI 904L technical data sheet, version 1 (2012)'
    id: ATI 904L TDS, version 1, 4/18/2012
    url: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/superaustenitic/ati_904l_tds_en_v1.pdf
    kind: datasheet
    year: 2012
    license: cited, not reproduced
  sandmeyer-904l:
    title: 'Sandmeyer Steel: Alloy 904L specification sheet (rev 02/2023)'
    id: Alloy 904L 11/2014, rev 02/2023
    url: https://www.sandmeyersteel.com/wp-content/uploads/Alloy904L-SpecSheet.pdf
    kind: datasheet
    year: 2023
    license: cited, not reproduced
  metalcor-1-4539:
    title: 'Metalcor: 1.4539 (AISI 904 L / N08904) datasheet'
    id: Metalcor datasheet 32
    url: http://www.metalcor.de/en/datenblatt/32/
    kind: datasheet
    license: cited, not reproduced
  wiki-sae904l:
    title: 'Wikipedia: SAE 904L stainless steel'
    id: SAE 904L stainless steel
    url: https://en.wikipedia.org/wiki/SAE_904L_stainless_steel
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  spacemat-904l:
    title: 'SpaceMat: AISI 904L entry'
    id: SpaceMat AISI 904L
    url: https://www.spacematdb.com/spacemat/datasearch.php?name=AISI+904L
    kind: database
    license: cited, not reproduced
  usgs-nickel-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Nickel'
    id: mcs2026-nickel
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-nickel.pdf
    kind: report
    year: 2026
    license: public domain
  usgs-chromium-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    id: mcs2026-chromium
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    kind: report
    year: 2026
    license: public domain
  usgs-molybdenum-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Molybdenum'
    id: mcs2026-molybdenum
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    kind: report
    year: 2026
    license: public domain
  usgs-copper-2026:
    title: 'USGS Mineral Commodity Summaries 2026: Copper'
    id: mcs2026-copper
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    kind: report
    year: 2026
    license: public domain
  pubchem-nickel:
    title: 'PubChem: 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 terms (public)
  pubchem-chromium:
    title: 'PubChem: Chromium (CID 23976), GHS classification'
    id: CID 23976
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23976/JSON
    kind: database
    license: PubChem terms (public)
  pubchem-molybdenum:
    title: 'PubChem: Molybdenum (CID 23932), GHS classification'
    id: CID 23932
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23932/JSON
    kind: database
    license: PubChem terms (public)
  pubchem-copper:
    title: 'PubChem: Copper (CID 23978), GHS classification'
    id: CID 23978
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23978/JSON
    kind: database
    license: PubChem terms (public)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 30
  unreachable: 0
  caveats: 4
  note: 'Read by an AI assistant on 2026-10-26 from pages fetched in this run: Outokumpu Ultra range datasheet (PDF), ATI 904L technical data sheet (PDF, 2012), Sandmeyer Steel Alloy 904L specification sheet (PDF), Metalcor 1.4539 datasheet, Wikipedia SAE 904L article, SpaceMat AISI 904L entry, USGS Mineral Commodity Summaries 2026 for nickel, chromium, molybdenum and copper, and PubChem GHS records for nickel, chromium, molybdenum and copper. Each value carries its product form, temperature and basis in conditions.'
story:
  why: 904L is a super-austenitic stainless steel. Its 20 percent chromium, 24 percent nickel and 4.3 percent molybdenum, with 1.4 percent copper, give a PRE of 34 and good resistance to sulfuric and phosphoric acids and to chloride pitting. It was developed for dilute sulfuric acid. Its minimum proof strength is 220 MPa to ASTM and 240 MPa for EN cold-rolled strip. Sold for acid plant, seawater cooling and pulp bleaching, it is a standard grade in the 904L class.
  uses:
    - where: Seawater and desalination
      line: Sandmeyer lists condensers, heat exchangers and piping for seawater and brackish water, and ATI lists tubesheets in seawater heat exchangers.
    - where: Acid and chemical plant
      line: Outokumpu lists pipes, heat exchangers, tanks and reactor vessels for sulfuric acid and the chemical industry, with flanges and valves.
    - where: Air pollution control
      line: Sandmeyer lists scrubbers for coal-fired power plants, and ATI lists utility scrubbers.
    - where: Pulp and paper bleaching
      line: ATI says 904L suits pulp and paper bleach plant equipment where some attack is tolerable.
  can_do:
    - label: Strength
      benchmark: yield_strength
      line: Minimum proof strength is 220 MPa to ASTM B625 for plate, sheet and strip, and 240 MPa to EN 10088-2 for cold-rolled strip. Tensile strength is 490 MPa minimum to ASTM.
    - label: Acid corrosion
      benchmark: corrosion_rate
      line: In wet process phosphoric acid at 60 °C, 904L corrodes at 1.2 mm/year, against more than 5 for 316L. In pickling acid at 25 °C it corrodes at 0.47 mm/year, against more than 6 for 316L.
    - label: Pitting
      benchmark: pren
      line: Outokumpu gives a PRE of 34 for Ultra 904L. Its critical crevice temperature in ATI's G-48 test is 18 °C.
    - label: Hot strength
      benchmark: yield_strength
      line: Minimum proof strength (Rp0.2) at 100 °C is 205 MPa, falling to 145 MPa at 300 °C and 110 MPa at 500 °C (EN 10088-2).
  compare: Against 316L in the same tests, 904L corrodes at 0.47 mm/year against more than 6 in pickling acid at 25 °C, and at 101 against 636 mpy in boiling 10 percent sulfuric acid. ATI's G-48 onset temperature is 18 °C for 904L against -3 °C for 316. Its minimum proof strength for plate (220 MPa, EN 10088-2) is below the 300 MPa minimum that Outokumpu prints for Ultra 254 SMO plate.
  compare_rows:
    - label: Proof strength (Rp0.2, minimum)
      benchmark: yield_strength
    - label: Tensile strength (Rm, minimum)
      benchmark: ultimate_tensile_strength
    - label: Pitting resistance (PRE)
      benchmark: pren
  handling:
    - Anneal at 1060 to 1140 °C and quench (Outokumpu Table 8; Sandmeyer hot forming).
    - Weld with low heat input and a 20 25 5 Cu L filler (Outokumpu Table 9). Sandmeyer says the same-composition filler is normal.
    - Machining is harder than for 304 or 410 because of work hardening (Sandmeyer).
  good_for:
    - Sulfuric and phosphoric acid plant, where Outokumpu lists pipes, heat exchangers, tanks and reactor vessels.
    - Seawater condensers and heat exchangers, where Sandmeyer lists tube and piping systems.
    - Pickling equipment and pulp and paper bleach plant, where ATI and Sandmeyer name the uses.
  watch_out:
    - Chloride cracking can occur in boiling magnesium or lithium chloride (ATI U-bend test).
    - Crevices start attack at 18 °C in ATI's G-48 test, so crevice design still matters in warm chloride water.
    - Acids containing halide ions can be very aggressive, and 904L may be insufficient (Sandmeyer).
    - No spacecraft flight use is recorded. SpaceMat rates the space experience as limited.
  verdict: 904L is a strong, sound choice for sulfuric and phosphoric acid plant, seawater cooling and pulp bleaching. It resists general and pitting attack better than 316L, but it is not immune to chloride cracking in boiling chloride, or to crevice and halide attack in warm chloride service.
  recipe:
    line: 904L is an iron-based super-austenitic stainless steel. Outokumpu's typical recipe, in weight percent, is 19.8 chromium, 24.2 nickel, 4.3 molybdenum, 1.4 copper and 0.01 carbon, with iron as the balance. The ASTM ranges are 19 to 23 chromium, 23 to 28 nickel, 4 to 5 molybdenum and 1 to 2 copper. It is solution annealed at 1060 to 1140 °C and quenched to give a fully austenitic structure.
    parts:
      - name: Iron
        symbol: Fe
        share_note: balance
        role: Matrix of the alloy, fully austenitic after annealing.
      - name: Chromium
        symbol: Cr
        share_percent: 19.8
        role: Forms the passive film. With molybdenum and nitrogen it sets the PRE.
        source: outokumpu-ultra
        where: Table 1, chemical composition, row Ultra 904L
      - name: Nickel
        symbol: Ni
        share_percent: 24.2
        role: Stabilises austenite and gives resistance to chloride cracking and to hot caustic.
        source: outokumpu-ultra
        where: Table 1, chemical composition, row Ultra 904L
      - name: Molybdenum
        symbol: Mo
        share_percent: 4.3
        role: Adds pitting and crevice resistance; weighted 3.3 in the PRE formula.
        source: outokumpu-ultra
        where: Table 1, chemical composition, row Ultra 904L
      - name: Copper
        symbol: Cu
        share_percent: 1.4
        role: Adds resistance to reducing acids such as sulfuric and phosphoric.
        source: outokumpu-ultra
        where: Table 1, chemical composition, row Ultra 904L
      - name: Carbon
        symbol: C
        share_note: max 0.02
        role: Kept low to limit chromium carbides in welds.
        source: sandmeyer-904l
        where: Chemical Analysis table, Carbon maximum
      - name: Manganese
        symbol: Mn
        share_note: max 2
        role: Deoxidiser in the melt.
        source: sandmeyer-904l
        where: Chemical Analysis table, Manganese maximum
      - name: Silicon
        symbol: Si
        share_note: max 1
        role: Deoxidiser in the melt.
        source: sandmeyer-904l
        where: Chemical Analysis table, Silicon maximum
  risk_groups:
    - title: For people
      level: 0
      verdict: No safety data sheet for the alloy was checked
      lead: The hazard data are PubChem records for the element nickel, chromium, molybdenum and copper, not a supplier classification of the alloy.
      points:
        - label: Nickel
          line: PubChem's record for elemental nickel lists H317, H351 and H372 as statements without a percentage.
        - label: Chromium
          line: PubChem's record for elemental chromium lists H317, H334 and H335.
        - label: Copper
          line: PubChem's record for elemental copper lists H400 and H410.
    - title: In chloride service
      level: 1
      verdict: Chloride cracking and crevices are the watch points
      lead: Boiling chloride can crack the alloy, and crevices start attack at warm temperatures.
      points:
        - label: Cracking
          line: ATI's U-bend test cracked 904L in boiling 42 percent MgCl2 and 33 percent LiCl within 1000 hours.
        - label: Crevice
          line: ATI's G-48 onset for 904L is 18 °C, against -3 °C for 316.
    - title: Fabrication
      level: 0
      verdict: Low heat input and a solution anneal
      lead: Weld with low heat input and a matching or overmatched filler. Anneal after hot work.
      points:
        - label: Welding
          line: Outokumpu says Ultra grades are more sensitive to hot cracking, so low heat input is needed.
        - label: Hot work
          line: Hot working at 1150 to 850 °C, then a solution anneal at 1060 to 1140 °C (Outokumpu Table 8).