spore: profile
id: stainless-304l
spore_version: 0.2
family: stainless-austenitic
name: Stainless steel 304L
abbreviation: 304L (UNS S30403)
role: corrosion-resistant structural alloy
category: metals
type: steels-and-stainless
summary: |
  Type 304L is the low-carbon form of 304, an austenitic chromium-nickel stainless steel. Its carbon limit of 0.030 percent maximum limits chromium carbide after welding, so the grade is specified for welded parts in corrosive service. The ASTM A240 minimums printed by ATI and ICAST are 485 MPa tensile and 170 MPa yield for plate, sheet and strip, and ATI gives a density of 7.90 g/cm3. Its main limits are sensitization after holds between 450 and 900 C, and chloride service, which Carpenter rates as restricted in sea water.
best_for: Welded parts in corrosive service, where the as-welded condition must resist carbide precipitation
weakest_at: 'Sea water and chloride service: Carpenter rates 304 and 304L restricted in sea water, and no pitting number for 304L was found'
identity:
  formula: Fe balance; 18.0 to 20.0 Cr, 8.0 to 12.0 Ni, max 0.030 C, max 2.00 Mn, max 0.75 Si, max 0.045 P, max 0.030 S, max 0.10 N (wt%). ATI prints 17.5 to 19.5 Cr for the same grade
  source: icast-s30403
  where: Chemical Composition table of the ICAST ASTM A240 UNS S30403 data sheet. Carpenter's 304L page gives Cr 18.00 to 20.00 (nominal). The ATI 304L page gives Cr 17.5 to 19.5
  designations:
    - system: UNS
      code: S30403
      source: ati-304l
      where: Title block of the ATI 304L page, UNS S30403
    - system: EN
      code: '1.4307'
      source: alleima-list
      where: Austenitic stainless steels table, Alleima 4LR11 row (UNS S30403, ASTM 304L, EN 1.4307)
    - system: EN
      code: '1.4306'
      source: alleima-list
      where: Austenitic stainless steels table, Alleima 3R12 row (UNS S30403, ASTM 304L, EN 1.4306)
    - system: EN name
      code: X2CrNi18-9
      source: alloys-intl-304l
      where: 304L entry, W.Nr 1.4307 followed by X2CrNi18-9
    - system: AISI
      code: 304L
      source: icast-s30403
      where: Cross Reference Table, row 304L with standard AISI
    - system: JIS
      code: SUS304L
      source: icast-s30403
      where: Cross Reference Table, row SUS 304L with standard JIS
    - system: BS
      code: 304 S 11
      source: icast-s30403
      where: Cross Reference Table, row 304 S 11 with standard BS
    - system: ASTM
      code: A240
      note: plate, sheet and strip; UNS S30403
      source: icast-s30403
      where: 'Title line, Material: ASTM A240 UNS S30403'
    - system: ASME
      code: SA-240
      note: plate, sheet and strip
      source: ati-304l
      where: Specifications line under Plate, Sheet and Strip
    - system: ASTM
      code: A666
      note: plate, sheet and strip
      source: ati-304l
      where: Specifications line under Plate, Sheet and Strip
    - system: ASTM
      code: A312
      note: seamless and welded pipe
      source: ati-tds-304l
      where: Specifications table, Seamless and/or Welded Pipe row
    - system: ASTM
      code: A182
      note: flanges and fittings
      source: ati-tds-304l
      where: Specifications table, Flanges and Fittings row
    - system: ASTM
      code: A276
      note: bar and wire
      source: ati-tds-304l
      where: Specifications table, Bar and Wire row
    - system: ASTM
      code: A479
      note: bar and wire
      source: ati-tds-304l
      where: Specifications table, Bar and Wire row
tags:
  environments: []
  stresses: []
  applications:
    - propulsion-and-tanks
    - structures
properties:
  - benchmark: density
    label: Density, plate, sheet and strip (ATI 304L page)
    value: 7.9
    unit: g/cm3
    scope: material
    conditions:
      form: plate, sheet and strip
      temperature: not stated
      temper: not stated
    method: Density row of the ATI 304L product page, metric value printed beside 0.285 lb/in3; the same value appears in each product form block
    status: ground
    source: ati-304l
    where: Density row, Plate block (the Sheet and Strip blocks print the same value)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength minimum, ASTM A240 (ATI 304L page)
    value: 485
    unit: MPa
    scope: material
    bound: lower
    conditions:
      form: plate, sheet and strip
      basis: minimum, printed as 70 ksi min and 485 MPa min
      temper: not stated
    method: Tensile Strength row of the ATI 304L product page, MPa value printed as 485 min
    status: ground
    source: ati-304l
    where: Tensile Strength row, Plate block
  - benchmark: yield_strength
    label: Yield strength minimum, ASTM A240 (ATI 304L page)
    value: 170
    unit: MPa
    scope: material
    bound: lower
    conditions:
      form: plate, sheet and strip
      basis: minimum, printed as 25 ksi min and 170 MPa min
      offset: not stated
      temper: not stated
    method: Yield Strength row of the ATI 304L product page, MPa value printed as 170 min
    status: ground
    source: ati-304l
    where: Yield Strength row, Plate block
  - benchmark: elongation
    label: Elongation minimum, ASTM A240 (ATI 304L page)
    value: 40
    unit: '%'
    scope: material
    bound: lower
    conditions:
      form: plate, sheet and strip
      basis: minimum as printed
      gauge_length: not stated
      temper: not stated
    method: Elongation row of the ATI 304L product page, printed as 40% min
    status: ground
    source: ati-304l
    where: Elongation row, Plate block
  - benchmark: hardness_rockwell_b
    label: Hardness maximum, Rockwell B (ATI 304L page)
    value: 92
    unit: HRB
    scope: material
    bound: upper
    conditions:
      form: plate, sheet and strip
      basis: maximum, printed as 92 HRB max
      temper: not stated
    method: Hardness row of the ATI 304L product page, printed as 92 HRB max
    status: ground
    source: ati-304l
    where: Hardness row, Plate block
  - benchmark: ultimate_tensile_strength
    label: Tensile strength minimum, ASTM A240 (ICAST S30403 sheet)
    value: 485
    unit: MPa
    scope: material
    bound: lower
    conditions:
      product: ASTM A240 plate, sheet and strip, UNS S30403
      heat_treatment: solution annealing, printed under the Heat Treatment column
      basis: minimum, printed as 485 min.
    method: Mechanical Properties block of the ICAST ASTM A240 UNS S30403 data sheet, Tensile Strength in MPa row
    status: ground
    source: icast-s30403
    where: Mechanical Properties, Tensile Strength in Mpa row
  - benchmark: yield_strength
    label: Yield strength minimum, ASTM A240 (ICAST S30403 sheet)
    value: 170
    unit: MPa
    scope: material
    bound: lower
    conditions:
      product: ASTM A240 plate, sheet and strip, UNS S30403
      heat_treatment: solution annealing, printed under the Heat Treatment column
      basis: minimum, printed as 170 min.
      offset: not stated
    method: Mechanical Properties block of the ICAST data sheet, Yield Strength in MPa row
    status: ground
    source: icast-s30403
    where: Mechanical Properties, Yield Strength in Mpa row
  - benchmark: elongation
    label: Elongation minimum, ASTM A240 (ICAST S30403 sheet)
    value: 40
    unit: '%'
    scope: material
    bound: lower
    conditions:
      product: ASTM A240 plate, sheet and strip, UNS S30403
      heat_treatment: solution annealing, printed under the Heat Treatment column
      basis: minimum, printed as 40 min.
      gauge_length: not stated
    method: Mechanical Properties block of the ICAST data sheet, Elongation in % row
    status: ground
    source: icast-s30403
    where: Mechanical Properties, Elongation in % row
  - benchmark: hardness_brinell
    label: Hardness maximum, Brinell (ICAST S30403 sheet)
    value: 201
    unit: HB
    scope: material
    bound: upper
    conditions:
      product: ASTM A240 plate, sheet and strip, UNS S30403
      heat_treatment: solution annealing, printed under the Heat Treatment column
      basis: maximum, printed as 201 max.
    method: Mechanical Properties block of the ICAST data sheet, Hardness in HB row
    status: ground
    source: icast-s30403
    where: Mechanical Properties, Hardness in HB row
  - benchmark: yield_strength
    label: Yield strength, 304L column (UPMET Alloy 304 sheet)
    value: 241
    unit: MPa
    scope: material
    conditions:
      column: 304L
      offset: 0.2%
      basis: table value; minimum or typical not stated
      temper: not stated
      unit_in_source: 35 (241) under header psi (MPa)
    method: Mechanical Properties table, 0.2% Offset Yield Strength row, 304L column; the MPa value in brackets is taken as printed
    status: ground
    source: upmet-304-304l
    where: Mechanical Properties of 304 table, 0.2% Offset Yield Strength row, 304L column
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, 304L column (UPMET Alloy 304 sheet)
    value: 586
    unit: MPa
    scope: material
    conditions:
      column: 304L
      basis: table value; minimum or typical not stated
      temper: not stated
      unit_in_source: 85 (586) under header psi (MPa)
    method: Mechanical Properties table, Ultimate Tensile Strength row, 304L column; the MPa value in brackets is taken as printed
    status: ground
    source: upmet-304-304l
    where: Mechanical Properties of 304 table, Ultimate Tensile Strength row, 304L column
  - benchmark: elongation
    label: Elongation, 304L column (UPMET Alloy 304 sheet)
    value: 55
    unit: '%'
    scope: material
    conditions:
      column: 304L
      gauge_length: 2 in (50.8 mm), as printed
      basis: table value; minimum or typical not stated
      temper: not stated
    method: Mechanical Properties table, Elongation row, 304L column
    status: ground
    source: upmet-304-304l
    where: Mechanical Properties of 304 table, Elongation in 2 in. row, 304L column
  - benchmark: hardness_rockwell_b
    label: Hardness, 304L column, Rockwell B (UPMET Alloy 304 sheet)
    value: 80
    unit: HRB
    scope: material
    conditions:
      column: 304L
      scale: Rockwell B, printed as B80
      basis: table value; minimum or typical not stated
      temper: not stated
    method: Mechanical Properties table, Hardness Rockwell row, 304L column, printed as B80
    status: ground
    source: upmet-304-304l
    where: Mechanical Properties of 304 table, Hardness Rockwell row, 304L column
  - benchmark: elastic_modulus
    label: Elastic modulus in tension (ATI shared table)
    value: 200
    unit: GPa
    scope: material
    conditions:
      loading: tension
      basis: printed as 29 x 10^6 psi (200 GPa) in one table shared by ATI 302, 304, 304L and 305
      temperature: not stated
    method: Physical Properties page of the ATI 302/304/304L/305 technical data sheet, Modulus of Elasticity in Tension row; the table is not split by grade
    status: ground
    source: ati-tds-304l
    where: Physical Properties, Modulus of Elasticity in Tension
  - benchmark: cte
    label: Mean coefficient of thermal expansion, 20 to 100 C (ATI shared table)
    value: 16.6
    unit: 10-6 cm/cm/°C
    scope: material
    conditions:
      temperature_range: 20 to 100 C (68 to 212 F)
      basis: mean coefficient; one table shared by ATI 302, 304, 304L and 305
    method: Linear Coefficient of Thermal Expansion table, cm/cm/°C column at 20 to 100 C
    status: ground
    source: ati-tds-304l
    where: Physical Properties, Linear Coefficient of Thermal Expansion, 20 to 100 C row
  - benchmark: cte
    label: Mean coefficient of thermal expansion, 20 to 870 C (ATI shared table)
    value: 19.8
    unit: 10-6 cm/cm/°C
    scope: material
    conditions:
      temperature_range: 20 to 870 C (68 to 1600 F)
      basis: mean coefficient; one table shared by ATI 302, 304, 304L and 305
    method: Linear Coefficient of Thermal Expansion table, cm/cm/°C column at 20 to 870 C
    status: ground
    source: ati-tds-304l
    where: Physical Properties, Linear Coefficient of Thermal Expansion, 20 to 870 C row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 100 C (ATI shared table)
    value: 16.3
    unit: W/m·K
    scope: material
    conditions:
      temperature: 100 C (212 F)
      basis: one table shared by ATI 302, 304, 304L and 305
    method: Thermal Conductivity table, W/m K column at 100 C
    status: ground
    source: ati-tds-304l
    where: Physical Properties, Thermal Conductivity, 212 F / 100 C row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 500 C (ATI shared table)
    value: 21.4
    unit: W/m·K
    scope: material
    conditions:
      temperature: 500 C (932 F)
      basis: one table shared by ATI 302, 304, 304L and 305
    method: Thermal Conductivity table, W/m K column at 500 C
    status: ground
    source: ati-tds-304l
    where: Physical Properties, Thermal Conductivity, 932 F / 500 C row
  - benchmark: specific_heat
    label: Specific heat, 0 to 100 C (ATI shared table)
    value: 500
    unit: J/kg·K
    scope: material
    conditions:
      temperature_range: 0 to 100 C (32 to 212 F)
      basis: one table shared by ATI 302, 304, 304L and 305
    method: Specific Heat table, J/kg K column for 0 to 100 C
    status: ground
    source: ati-tds-304l
    where: Physical Properties, Specific Heat, 32 to 212 F / 0 to 100 C row
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 20 C (ATI shared table)
    value: 72
    unit: microhm-cm
    scope: material
    conditions:
      temperature: 20 C (68 F)
      basis: one table shared by ATI 302, 304, 304L and 305
    method: Electrical Resistivity table, Microhm-cm column at 20 C
    status: ground
    source: ati-tds-304l
    where: Electrical Resistivity table, 68 F / 20 C row
  - benchmark: melting_point
    label: Melting range (ATI shared table)
    value: 1399
    value_high: 1421
    bound: range
    unit: °C
    scope: material
    conditions:
      basis: melting range as printed, 2,550 to 2,590 F
      temperature: not applicable
    method: Melting Range table, range printed in C and F; the C values are taken as printed
    status: ground
    source: ati-tds-304l
    where: Melting Range table, 2,550 to 2,590 F / 1,399 to 1,421 C row
  - benchmark: max_service_temp
    label: Maximum use temperature, ASME coverage for ATI 304L
    value: 426
    unit: °C
    scope: material
    bound: upper
    conditions:
      basis: 'ASME Section II Part D coverage limit printed for ATI 304L: maximum use temperature 800 F (426 C), with lower allowable stresses than 304'
      temperature: not applicable
    method: Specifications and Certificates section (page 2) of the ATI 302/304/304L/305 data sheet, ASME paragraph; a code coverage limit, not a melting or oxidation limit
    status: ground
    source: ati-tds-304l
    where: Specifications and Certificates, ASME paragraph
  - benchmark: cte
    label: Mean coefficient of thermal expansion, 32 to 1200 F (CarTech 304/304L sheet)
    value: 10.4
    unit: 10-6 in/in/°F
    scope: material
    conditions:
      temperature_range: 32 to 1200 F (printed in F only)
      basis: mean CTE; combined 304 and 304L data sheet
    method: Physical Properties block, Mean CTE row, printed in imperial units only and not converted
    status: ground
    source: carpenter-304-304l-datasheet
    where: Physical Properties, Mean CTE (32 to 1200 F) row
  - benchmark: safe_scaling_temperature
    label: Safe scaling temperature for continuous service (CarTech 304/304L sheet)
    value: 871
    unit: °C
    scope: material
    bound: upper
    conditions:
      basis: continuous service, printed as 1600 F (871 C)
      temperature: continuous service
    method: Scaling section, safe scaling temperature for continuous service, printed in F with C in brackets
    status: ground
    source: carpenter-304-304l-datasheet
    where: Scaling section
  - benchmark: hardness_brinell
    label: Hardness after annealing, Brinell (CarTech 304/304L sheet)
    value: 150
    unit: HB
    scope: material
    conditions:
      temper: 'annealed: heat to 1010/1121 C (1850/2050 F) and quench in water'
      basis: printed as approximately 150; a typical value, not a limit
    method: Heat Treatment, Annealing paragraph, Brinell hardness printed as approximately 150
    status: ground
    source: carpenter-304-304l-datasheet
    where: Heat Treatment, Annealing paragraph
  - benchmark: hydrogen_outgassing_rate
    label: Hydrogen outgassing rate of an unfired 304L vacuum chamber
    value: 9.4
    unit: ×10-10 Pa L s-1 cm-2
    scope: material
    uncertainty: 24 percent (uQH2 for the 304L chamber)
    conditions:
      chamber: unfired 304L chamber, no vacuum-fire heat treatment
      temperature: 298.15 K
      pre_bake: 125 to 150 C for at least 72 h before rate-of-rise measurement
      basis: Table IV value, printed as 9.4 x 10-10 with the exponent kept in the unit
    method: Table IV of the NIST paper, QH2 at 298.15 K, determined from the fitting parameters A0 and ED for the non-titanium chambers; the value is for one chamber made of 304L, not a bulk-material test
    status: calculated
    note: Table IV gives a relative improvement factor of 184 for the vacuum-fired 316L-XHV chamber against the 304L chamber. The abstract's range of 4.0 to 8.0 x 10-11 covers the unfired 304L, 316L and 316LN chambers together and is not split by grade, so it is not recorded as a 304L value.
    source: nist-vacuum-2020
    where: Table IV, row 304L (QH2 at 298.15 K column); abstract for bake conditions
corrosion:
  - environment: Sea water
    headline: Carpenter rates 304 and 304L restricted in sea water on its comparative scale. No pitting or critical temperature for 304L was found.
    effect: The CarTech 304/304L data sheet lists Sea Water as Restricted on a four-level comparative scale and says corrosion testing is recommended, because temperature, concentration, pH, crevices, deposits and surface finish all affect resistance.
    rating: unknown
    conditions:
      printed_rating: Restricted
      scale: four-level comparative scale, comparison only
      basis: the data sheet covers 304 and 304L together
    source: carpenter-304-304l-datasheet
    where: Corrosion Resistance table, Sea Water row, and the Important Note
  - environment: Salt spray (NaCl)
    headline: Carpenter rates salt spray Good for 304 and 304L, in contrast with the restricted rating for sea water.
    effect: On the same comparative scale, salt spray (sodium chloride) is rated Good. The sheet calls the scale comparative only.
    rating: low
    conditions:
      printed_rating: Good
      basis: comparative scale, no test conditions given
    source: carpenter-304-304l-datasheet
    where: Corrosion Resistance table, Salt Spray (NaCl) row
  - environment: Warm chloride environments and chloride stress corrosion
    headline: Wikipedia says 304, which it also says has the same corrosion resistance as 304L, is subject to pitting and crevice corrosion in warm chlorides.
    effect: Wikipedia says 304 is subject to pitting and crevice corrosion in warm chloride environments and to stress corrosion cracking above about 60 C (140 F). It says 316 is commonly used in place of 304 when chloride pitting or crevice corrosion is too severe. The article is about 304, so these statements are a 304 comparison, not 304L values.
    rating: moderate
    conditions:
      temperature: stress corrosion cracking above about 60 C (140 F), as printed for 304
      basis: Wikipedia corrosion section for 304; the article says 304, 304H and 304L have the same corrosion resistance
    source: wiki-304
    where: Corrosion resistance section of the 304 stainless steel article; Carbon content section
  - environment: Nitric acid
    headline: Carpenter rates nitric acid Good for 304 and 304L on its comparative scale.
    effect: On the CarTech 304/304L comparative scale, nitric acid is rated Good. The sheet says the four-level ratings are for comparison and recommends corrosion testing, because concentration and temperature change the result.
    rating: low
    conditions:
      printed_rating: Good
      concentration: not stated
      temperature: not stated
    source: carpenter-304-304l-datasheet
    where: Corrosion Resistance table, Nitric Acid row
  - environment: Sulfuric acid
    headline: Carpenter rates sulfuric acid Moderate for 304 and 304L on its comparative scale.
    effect: The same comparative table rates sulfuric acid Moderate, as it does phosphoric acid, acetic acid, sodium hydroxide and sour oil or gas. Each is a comparison, not a limit.
    rating: moderate
    conditions:
      printed_rating: Moderate
      concentration: not stated
      temperature: not stated
    source: carpenter-304-304l-datasheet
    where: Corrosion Resistance table, Sulfuric Acid row
  - environment: Heating or slow cooling through 450 to 900 C, as in a weld heat-affected zone
    headline: Chromium carbide forms at grain boundaries in this range. The 0.030 percent carbon maximum of 304L limits it.
    effect: Thermal Processing says chromium carbide precipitates at grain boundaries between 450 and 900 C when carbon is above about 0.02 percent. It says the L designation holds carbon below 0.030 percent to improve weldability and limit chromium carbide. Wikipedia gives a sensitization range of 480 to 820 C and a 0.035 percent maximum for 304L, which differs from the 0.030 percent printed on the datasheets.
    rating: moderate
    conditions:
      temperature: 450 to 900 C (Thermal Processing); 480 to 820 C (Wikipedia)
      carbon_threshold: above about 0.02 percent
      carbon_limit_L: below 0.030 percent
      basis: general austenitic steel statement that applies to the L designation
    source: thermal-processing
    where: Sensitization of Austenitic Stainless Steels, Introduction and L designation paragraphs
  - environment: Welded structures in the most severe corrosive service
    headline: Carpenter says welds keep their corrosion resistance, but the welded structure should be reannealed for the most severe environments.
    effect: The CarTech 304/304L data sheet says the alloy can be welded without loss of corrosion resistance from intergranular carbide precipitation and is usually used in the as-welded condition. For service in the most severe environments it advises reannealing the welded structure.
    rating: unknown
    conditions:
      condition: as-welded, or reannealed for the most severe service
      basis: qualitative statement, no test conditions given
    source: carpenter-304-304l-datasheet
    where: Weldability section
risks:
  hazards:
    - text: 'PubChem aggregated GHS for elemental nickel (CID 935, signal Danger): H317 May cause an allergic skin reaction; H351 Suspected of causing cancer; H372 Causes damage to organs through prolonged or repeated exposure. PubChem reports that 0.1 percent (5 of 4,778) of company reports say it does not meet GHS criteria. The data cover the element, not the alloy.'
      ghs:
        - H317
        - H351
        - H372
      source: pubchem-nickel
      where: Safety and Hazards, GHS Classification (aggregated), CID 935
    - text: 'PubChem aggregated GHS for elemental chromium (CID 23976, signal Danger): H317 (20.7 percent notified ratio) May cause an allergic skin reaction; H319 (19.1 percent) Causes serious eye irritation; H334 (20.3 percent) May cause allergy or asthma symptoms or breathing difficulties if inhaled. Half of 2,404 reports (1,202) say it does not meet GHS criteria. The data cover the element, not the alloy.'
      ghs:
        - H317
        - H319
        - H334
      source: pubchem-chromium
      where: Safety and Hazards, GHS Classification (aggregated), CID 23976
  failure_risks:
    - mode: Intergranular (sensitization) corrosion after welding or slow cooling
      trigger: Holding or slow cooling between 450 and 900 C, as in a weld heat-affected zone
      consequence: Chromium carbide at grain boundaries leaves the boundary open to attack. The 0.030 percent carbon maximum makes this much less likely than in 304, which Wikipedia gives a 0.08 percent carbon maximum.
      severity: moderate
      source: thermal-processing
      where: Sensitization of Austenitic Stainless Steels
    - mode: Pitting, crevice and chloride stress corrosion in sea water
      trigger: Sea water service, which Carpenter rates as restricted for 304 and 304L
      consequence: The datasheets read give no critical pitting temperature or chloride limit for 304L. Carpenter recommends corrosion testing before use in this service.
      severity: high
      source: carpenter-304-304l-datasheet
      where: Corrosion Resistance table, Sea Water row, and the Important Note
    - mode: Hydrogen outgassing in ultra-high vacuum
      trigger: Unfired 304L chamber after a 125 to 150 C bake for at least 72 hours
      consequence: The NIST fit gives 9.4 x 10-10 Pa L s-1 cm-2 at 298.15 K for 304L (Table IV). The vacuum-fired 316L-XHV chamber is listed with a relative improvement factor of 184 over 304L.
      severity: moderate
      source: nist-vacuum-2020
      where: Table IV, rows 304L and 316L-XHV; abstract for the bake conditions
  side_effects: []
  handling:
    - text: Specify 304L rather than 304 for welded parts in corrosive service. Wikipedia says 304, with a 0.08 percent carbon maximum, is not useful where welding is required, and that 304L is preferred.
      source: wiki-304
      where: Carbon content section
    - text: Anneal at 1010 to 1121 C (1850 to 2050 F) and quench in water. Forgings must be annealed for full corrosion resistance.
      source: carpenter-304-304l-datasheet
      where: Heat Treatment, Annealing paragraph, and Forging section
    - text: Reanneal welded structures that will see the most severe environments, as Carpenter advises.
      source: carpenter-304-304l-datasheet
      where: Weldability section
    - text: The ATI and ICAST datasheets give ASTM A240 minimums only. Check the mill certificate for the form and temper being bought.
      source: ati-304l
      where: Tensile, Yield and Elongation rows (minimum values)
    - text: Cold work raises magnetic permeability. The 18-8 alloys are generally non-magnetic in the annealed condition, according to the ATI data sheet.
      source: ati-tds-304l
      where: Magnetic Permeability section
  mitigations:
    - text: For ultra-high vacuum, NIST vacuum-fired 316L and 316LN at about 950 C for 24 hours under vacuum. No vacuum-fired 304L chamber was tested, so the vacuum-firing benefit is not claimed for 304L.
      source: nist-vacuum-2020
      where: Abstract, vacuum-fire process and chamber list
    - text: Use the low-carbon grade in welds. The 0.030 percent carbon maximum limits carbide precipitation during welding, according to Carpenter.
      source: carpenter-304l
      where: Opening description, 304L page
uses:
  - application: propulsion-and-tanks
    device: Starship SN7 test tank and Starship SN8 prototype
    example: Wikipedia says early Starships used SAE 301 stainless steel, then SAE 304L for the SN7 test tank and Starship SN8 in 2020. This is a use report, not a test result for the alloy.
    source: wiki-304
    where: Applications section, Starship sentence
  - application: structures
    device: Vacuum chamber walls (laboratory)
    example: NIST chose 304L as its benchmark because it is one of the most commonly used materials for vacuum chambers in the United States. Table IV gives 9.4 x 10-10 Pa L s-1 cm-2 at 298.15 K for its unfired 304L chamber.
    source: nist-vacuum-2020
    where: Introduction, benchmark paragraph; Table IV
  - application: structures
    device: Welded products in corrosive service
    example: ATI says 304L is used for welded products that might be exposed to conditions which could cause intergranular corrosion in service.
    source: ati-tds-304l
    where: Introduction, ATI 304L paragraph
media: []
supply:
  - subject: Nickel
    abundance: Stainless and alloy steel plus nickel-containing alloys typically account for more than 85 percent of US domestic consumption. World reserves are more than 140,000,000 t, of which Indonesia holds 62,000,000 t (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 accounted for about 60 percent of US apparent consumption in 2025, and most recycled nickel goes into new alloys and stainless steel (USGS 2026).
    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), Domestic Production and Use, Recycling and Substitutes. Shares are computed from the 3,900,000 t 2025e world total
  - subject: Nickel import reliance, United States
    abundance: US net import reliance was 41 percent of apparent consumption in 2025 (estimated) (USGS 2026).
    producers: []
    critical_lists: []
    recycling: Recycled nickel was about 60 percent of apparent consumption in 2025.
    substitutes: []
    source: usgs-nickel-2026
    where: Salient Statistics, net import reliance row (2025e)
  - subject: Chromium
    abundance: World resources are greater than 12 billion t of shipping-grade chromite, and 95 percent of world chromium resources lie in Kazakhstan and southern Africa (USGS 2026).
    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 (USGS 2026).
    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, gross weight). Shares are computed from the 51,000 thousand t world total. Substitutes and Recycling
  - subject: Chromium import reliance, United States
    abundance: 'US net import reliance was 79 percent of apparent consumption in 2025 (estimated). Chromite imports 2021 to 2024: South Africa 96 percent, Turkey 3 percent (USGS 2026).'
    producers: []
    critical_lists: []
    recycling: Recycled chromium was 21 percent of apparent consumption in 2025.
    substitutes: []
    source: usgs-chromium-2026
    where: Salient Statistics, net import reliance row; Import Sources (2021 to 2024)
  - subject: Critical-mineral status
    abundance: Nickel and chromium are both on the USGS 2025 List of Critical Minerals (60 minerals). The list describes chromium as used in stainless steel and nickel as used to make high-strength steel and rechargeable batteries.
    producers: []
    critical_lists:
      - list: 'USGS 2025 List of Critical Minerals: nickel'
        listed: true
      - list: 'USGS 2025 List of Critical Minerals: chromium'
        listed: true
    substitutes: []
    source: usgs-crit-2025
    where: List entries on the About the 2025 List of Critical Minerals page (Chromium and Nickel rows). The EU critical raw materials list was not fetched
documents:
  - title: ATI 304L Austenitic Stainless Steel, UNS S30403 (product page)
    type: datasheet
    url: https://atimaterials.com/Products/ati-304l
  - title: ATI 302, 304, 304L and 305 Technical Data Sheet (version 1, 2014)
    type: datasheet
    url: https://atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/austenitic/ati_302_304_304l_305_tds_en3_v1.pdf
    year: 2014
  - title: 'ICAST Alloys: ASTM A240 UNS S30403 data sheet'
    type: datasheet
    url: https://www.icastllp.com/material_db_pdf/ASTM%20A240%20UNS%20S30403.pdf
  - title: 'Carpenter Technology: 304L alloy page (type analysis, applicable specifications)'
    type: datasheet
    url: https://www.carpentertechnology.com/alloy-finder/304L
  - title: CarTech 304/304L Stainless data sheet (Carpenter Technology)
    type: datasheet
    url: https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/304L.pdf
  - title: 'UPMET datasheet: Alloy 304 Stainless Steel Sheet, Coil and Plate (AMS 5511, 5513), with a 304L mechanical column'
    type: datasheet
    url: https://www.upmet.com/sites/default/files/datasheets/304-304l.pdf
    year: 2026
  - title: 'Alleima: list of alloys (billets and blooms), grade table with UNS, ASTM and EN steel numbers'
    type: datasheet
    url: https://www.alleima.com/cz/products/billets-and-blooms/list-of-alloys
  - title: 'Alloys International: stainless steel 304L page (W.Nr and EN names)'
    type: datasheet
    url: https://alloysintl.com/inventory/stainless-steel/stainless_steel304L/
  - title: 'Fedchak et al.: Outgassing rate comparison of seven geometrically similar vacuum chambers of different materials and heat treatments (arXiv:2009.10560)'
    type: paper
    url: https://arxiv.org/pdf/2009.10560
    year: 2020
  - 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: About the 2025 List of Critical Minerals'
    type: report
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
  - title: 'PubChem: Nickel (CID 935), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/935
  - title: 'PubChem: Chromium (CID 23976), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23976
gaps:
  - No Outokumpu, Aperam, Aalco or Combined Metals 304L datasheet was fetched. The one Combined Metals URL tried returned not found, no Aalco or Outokumpu 304L URL was known, and web search was unavailable in this session.
  - Physical properties (modulus, CTE, thermal conductivity, specific heat, resistivity, melting range) are printed in ATI's table for ATI 302, 304, 304L and 305 together, not split by grade. The CarTech 304/304L sheet is also combined. No 304L-only physical-property sheet was found.
  - 'Chromium range: ATI''s 304L page and technical data sheet print 17.5 to 19.5 weight percent. ICAST''s ASTM A240 sheet and Carpenter print 18.0 to 20.0. The recipe uses 18.0 to 20.0, and the disagreement is not resolved.'
  - 'Silicon maximum: Carpenter prints 1 (1.00 on its data sheet), against 0.75 on the ATI and ICAST sheets. The 0.75 value is used.'
  - 'Carbon: Wikipedia gives a 0.035 percent maximum for 304L, while the ATI, ICAST and Carpenter sheets print 0.030 percent maximum. The datasheet value is used.'
  - 'Outgassing: NIST''s abstract gives 4.0 to 8.0 x 10-11 Pa L s-1 cm-2 for the unfired 304L, 316L and 316LN chambers together. That range is not split by grade, so only the Table IV value for 304L alone is recorded. The NIST chamber composition for 304L (one heat, with molybdenum 0.28 to 0.43) is not the grade limit and is not used.'
  - UPMET's datasheet is headed Alloy 304 (UNS S30400). Only its 304L mechanical column is used. Its 304 composition and physical properties are not used. The 304L column does not state temper or whether the values are typical or minimum.
  - 'Hardness: ATI gives 92 HRB maximum and ICAST gives 201 HB maximum (both ASTM A240 limits). Carpenter gives an annealed Brinell of about 150 (typical). UPMET gives Rockwell B80 for 304L, with the basis not stated.'
  - Wikipedia gives the minimum tensile strength of 304L as 34 MPa (5,000 psi) below that of 304. The comparison appears in the story only, not as a 304L property.
  - Magnetic permeability values in the ATI table print no unit, so they are left out. The 304L column of that table shows the rise with cold work, which is noted in handling.
  - Pitting resistance equivalent number, critical pitting temperature and chloride limits for 304L were not found on the pages fetched. Sea water is only rated Restricted by Carpenter.
  - Sigma phase and 650 C embrittlement data for 304L were not found. The sigma-phase study used for 316L is not for this grade.
  - 'Designations: the grade names F304L (ASTM A182) and TP304L (ASTM A312) are not printed on the pages fetched, so those entries carry the specification number only. The EN name X2CrNi19-11 for EN 1.4306 was not printed on any page fetched. GOST 04CH18N10, printed on ICAST''s cross-reference row, was not added. Alleima trade grades 4LR11 and 3R12 are not used as designations.'
  - 'Critical minerals: the EU critical raw materials list was not fetched.'
  - 'Hazards: PubChem records are for elemental nickel and chromium, not for the alloy. No 304L safety data sheet with a GHS classification was fetched. Welding fume hazard was not sourced.'
  - 'Vacuum firing: NIST did not vacuum-fire a 304L chamber, so no vacuum-fired 304L value is recorded.'
  - No flight, space-thermal, radiation or cryogenic test result for 304L was found. The SpaceX tank use is a Wikipedia statement about use, not a test.
  - 'Sensitization range differs between sources: 450 to 900 C (Thermal Processing) and 480 to 820 C (Wikipedia). Both are kept with their source.'
  - The CarTech 304/304L sheet gives typical or average values and does not guarantee maximum or minimum values. Its edition date is printed as 07/01/2000 with a 2020 copyright.
  - The USGS critical-minerals page returned HTTP 403 to a plain curl agent and was read with a browser user agent. The verification step cannot reach it, but no property cites it.
  - 'Benchmarks not in property-canon, used as short snake_case names: hardness_rockwell_b, hardness_brinell, hydrogen_outgassing_rate and safe_scaling_temperature. Hardness and outgassing are not in the canonical list; the printed units are kept as printed.'
sources:
  ati-304l:
    title: ATI 304L Austenitic Stainless Steel, UNS S30403 (product page)
    id: ATI product page, 304L
    url: https://atimaterials.com/Products/ati-304l
    kind: datasheet
    license: ATI web page (cited, not reproduced)
  ati-tds-304l:
    title: ATI 302, 304, 304L and 305 Technical Data Sheet (version 1, 2014)
    id: ATI TDS, version 1 (2/17/2014)
    url: https://atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/austenitic/ati_302_304_304l_305_tds_en3_v1.pdf
    year: 2014
    kind: datasheet
    license: supplier data sheet (cited, not reproduced)
  icast-s30403:
    title: 'ICAST Alloys: ASTM A240 UNS S30403 data sheet, chemical composition, mechanical properties and cross reference'
    id: ASTM A240 UNS S30403
    url: https://www.icastllp.com/material_db_pdf/ASTM%20A240%20UNS%20S30403.pdf
    kind: datasheet
    license: stockist data sheet (cited, not reproduced)
  carpenter-304l:
    title: 'Carpenter Technology: 304L alloy page (type analysis, applicable specifications)'
    id: 304L alloy finder page
    url: https://www.carpentertechnology.com/alloy-finder/304L
    kind: datasheet
    license: manufacturer web page (cited, not reproduced)
  carpenter-304-304l-datasheet:
    title: CarTech 304/304L Stainless data sheet (Carpenter Technology, combined 304 and 304L)
    id: CarTech 304/304L Stainless, edition date 07/01/2000, copyright 2020
    url: https://www.carpentertechnology.com/hubfs/7407324/Material%20Saftey%20Data%20Sheets/304L.pdf
    kind: datasheet
    license: manufacturer data sheet (cited, not reproduced)
  upmet-304-304l:
    title: 'UPMET datasheet: Alloy 304 Stainless Steel Sheet, Coil and Plate (AMS 5511, 5513), with a 304L mechanical column'
    id: UNS S30400, AMS 5513
    url: https://www.upmet.com/sites/default/files/datasheets/304-304l.pdf
    year: 2026
    kind: datasheet
    license: supplier data sheet (cited, not reproduced)
  alleima-list:
    title: 'Alleima: list of alloys (billets and blooms), grade table with UNS, ASTM and EN steel numbers'
    id: Alleima list of alloys
    url: https://www.alleima.com/cz/products/billets-and-blooms/list-of-alloys
    kind: datasheet
    license: web page (cited, not reproduced)
  alloys-intl-304l:
    title: 'Alloys International: stainless steel 304L page (W.Nr and EN names)'
    id: stainless_steel304L page
    url: https://alloysintl.com/inventory/stainless-steel/stainless_steel304L/
    kind: datasheet
    license: stockist web page (cited, not reproduced)
  wiki-304:
    title: 'Wikipedia: 304 stainless steel (carbon content, applications, corrosion resistance)'
    id: 304 stainless steel
    url: https://en.wikipedia.org/wiki/304_stainless_steel
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  thermal-processing:
    title: 'Thermal Processing: Intergranular Corrosion of Austenitic Stainless Steels'
    id: thermalprocessing.com
    url: https://thermalprocessing.com/intergranular-corrosion-of-austenitic-stainless-steels/
    kind: web
    license: web page (cited, not reproduced)
  nist-vacuum-2020:
    title: 'Fedchak et al.: Outgassing rate comparison of seven geometrically similar vacuum chambers of different materials and heat treatments'
    id: arXiv:2009.10560 (DOI 10.1116/6.0000657)
    url: https://arxiv.org/pdf/2009.10560
    year: 2020
    kind: paper
    license: arXiv preprint (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
    year: 2026
    kind: report
    license: public domain (USGS)
  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-crit-2025:
    title: 'USGS: About the 2025 List of Critical Minerals'
    id: 2025 List of Critical Minerals, November 2025
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  pubchem-nickel:
    title: 'PubChem: Nickel (CID 935), Safety and Hazards, GHS Classification'
    id: CID 935
    url: https://pubchem.ncbi.nlm.nih.gov/compound/935
    kind: database
    license: PubChem terms (public)
  pubchem-chromium:
    title: 'PubChem: Chromium (CID 23976), Safety and Hazards, GHS Classification'
    id: CID 23976
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23976
    kind: database
    license: PubChem terms (public)
license: CC-BY-4.0
updated: '2026-10-24'
review:
  status: draft
  method: assistant
  checked_values: 26
  unreachable: 0
  caveats: 6
  note: Written by an AI assistant on 2026-10-24 from pages fetched that day. Web search was unavailable, so datasheet pages were fetched directly with curl. The physical properties come from the ATI 302/304/304L/305 table and the CarTech 304/304L sheet, which are shared with other grades. The UPMET 304L values come from a column on an Alloy 304 sheet.
story:
  recipe:
    line: 304L is an iron-based austenitic stainless steel. The ICAST ASTM A240 sheet for UNS S30403 gives 18 to 20 percent chromium and 8 to 12 percent nickel, with carbon at 0.030 percent maximum and iron as the balance. The ATI 304L page gives a narrower chromium range of 17.5 to 19.5 percent, in weight percent. No melting or process route for the alloy was found on the pages fetched.
    parts:
      - name: Iron
        symbol: Fe
        share_note: balance
        role: The matrix of the alloy.
      - name: Chromium
        symbol: Cr
        share_percent: 18
        share_high: 20
        role: Gives the stainless corrosion resistance. The 18-8 family is named for about 18 percent chromium (ATI). ATI prints 17.5 to 19.5 for the same grade.
      - name: Nickel
        symbol: Ni
        share_percent: 8
        share_high: 12
        role: With chromium, makes the 18-8 austenitic family (ATI).
      - name: Carbon
        symbol: C
        share_percent: 0
        share_high: 0.03
        role: Maximum 0.030 percent. Kept low so that chromium carbide does not form at grain boundaries after welding.
      - name: Manganese
        symbol: Mn
        share_percent: 0
        share_high: 2
        role: Maximum 2.00 percent. Impurity and processing element held to a maximum.
      - name: Silicon
        symbol: Si
        share_percent: 0
        share_high: 0.75
        role: Maximum 0.75 percent.
      - name: Phosphorus
        symbol: P
        share_percent: 0
        share_high: 0.045
        role: Maximum 0.045 percent. Impurity held low.
      - name: Sulfur
        symbol: S
        share_percent: 0
        share_high: 0.03
        role: Maximum 0.030 percent. Impurity held low.
      - name: Nitrogen
        symbol: 'N'
        share_percent: 0
        share_high: 0.1
        role: Maximum 0.10 percent.
  risk_groups:
    - title: For people
      level: 1
      verdict: Element data only, no alloy record
      lead: No safety data sheet with a GHS classification for the 304L alloy was fetched. The PubChem records below are for elemental nickel and chromium.
      points:
        - label: Nickel
          line: 'PubChem lists elemental nickel as Danger: H317 (skin sensitiser), H351 (suspected carcinogen) and H372 (organ damage on repeated exposure).'
        - label: Chromium
          line: PubChem lists elemental chromium with H317, H319 and H334 in notifications that carry hazard codes. Half of the 2,404 reports say it does not meet GHS criteria.
        - label: Cutting and welding
          line: Cutting, grinding and welding stainless steel can release metal fume and dust. No fume source was fetched, so check the supplier safety data sheet before work.
    - title: Welding and heat
      level: 2
      verdict: Low carbon limits sensitization
      lead: Sensitization is the main fabrication risk, and the low carbon of 304L is there to limit it.
      points:
        - label: Range
          line: Holding or slow cooling between 450 and 900 C precipitates chromium carbide at grain boundaries (Thermal Processing). Wikipedia gives 480 to 820 C.
        - label: Fix
          line: The carbon limit is 0.030 percent maximum. Carpenter says this minimises carbide precipitation during welding.
        - label: Severe service
          line: For the most severe environments, Carpenter advises reannealing the welded structure.
    - title: In sea water
      level: 3
      verdict: Restricted in sea water
      lead: Chloride is the watch point. Carpenter rates 304 and 304L restricted in sea water on its comparative scale.
      points:
        - label: Sea water
          line: Carpenter's comparative scale rates sea water as Restricted and recommends corrosion testing.
        - label: Chloride
          line: Wikipedia says 304, which it describes as having the same corrosion resistance as 304L, is subject to pitting and crevice corrosion in warm chloride and to stress corrosion cracking above about 60 C.
  why: Type 304L is the low-carbon version of the 18-8 austenitic stainless steel, the most frequently used alloy in the stainless family (ATI). Its carbon limit of 0.030 percent is there to limit chromium carbide after welding, so the grade is chosen for welded parts that must resist corrosion. Carpenter describes it as suited to the as-welded condition in corrosive applications, and lists food processing and dairy equipment for 304 and 304L. NIST chose it as the benchmark for vacuum chambers, and SpaceX moved to 304L for its Starship SN7 test tank and SN8 prototype.
  uses:
    - where: Starship test tank and prototype
      line: Wikipedia says early Starships used an earlier stainless grade, then SAE 304L for the SN7 test tank and Starship SN8 in 2020. That is a use report, not a test result for the alloy.
    - where: Vacuum chambers
      line: NIST benchmarked against 304L, one of the most commonly used materials for vacuum chambers in the United States. Its unfired 304L chamber had a hydrogen outgassing rate of 9.4 x 10-10 Pa L s-1 cm-2 at 298.15 K (Table IV).
    - where: Welded corrosive service
      line: ATI says 304L is used for welded products that might be exposed to conditions which could cause intergranular corrosion in service.
  can_do:
    - label: Strength
      benchmark: ultimate_tensile_strength
      line: ASTM A240 minimums for plate, sheet and strip are 485 MPa tensile and 170 MPa yield, with elongation of at least 40 percent (ATI and ICAST). The ATI maximum hardness is 92 HRB.
    - label: Density
      benchmark: density
      line: Density is 7.90 g/cm3 on the ATI 304L page.
    - label: Heat
      benchmark: melting_point
      value: 1399 to 1421 C
      line: The melting range is 1,399 to 1,421 C in ATI's table, which covers 302, 304, 304L and 305 together.
    - label: Vacuum
      benchmark: hydrogen_outgassing_rate
      value: 9.4 x 10-10 Pa L s-1 cm-2
      line: In NIST's Table IV, an unfired 304L chamber has a hydrogen outgassing rate of 9.4 x 10-10 Pa L s-1 cm-2 at 298.15 K. The table gives a relative improvement factor of 184 for the vacuum-fired 316L-XHV chamber against 304L.
  compare: 'Wikipedia says 304, 304H and 304L share the same nominal chromium and nickel content and the same corrosion resistance. The difference is carbon: Wikipedia gives a maximum of 0.08 percent for 304 and 0.035 percent for 304L, while the datasheets print 0.030 percent for 304L. Wikipedia also says the specified minimum tensile strength of 304L is 34 MPa (5,000 psi) lower than that of 304. The physical values in this profile come from tables that cover 304L together with other grades.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Tensile strength (minimum)
      benchmark: ultimate_tensile_strength
    - label: Melting range
      benchmark: melting_point
  handling:
    - Specify 304L rather than 304 for welded parts in corrosive service. Wikipedia says 304 is not useful where welding is required, and that 304L is preferred.
    - Anneal at 1010 to 1121 C and quench in water. Forgings must be annealed for full corrosion resistance (Carpenter).
    - Avoid holding 304L between 450 and 900 C during fabrication or service, because chromium carbide forms in that range.
    - For ultra-high vacuum, the NIST vacuum-firing benefit was tested on 316L and 316LN, not 304L. Check the mill certificate for the form and temper being bought.
  good_for:
    - Welded, corrosion-resistant parts in the as-welded condition, where carbide precipitation at the weld must be limited (Carpenter).
    - Food, dairy and processing equipment, which Carpenter lists for 304 and 304L (pipelines, buckets, sterilizers).
    - Vacuum chambers where the outgassing of an unfired 304L chamber, 9.4 x 10-10 Pa L s-1 cm-2 at 298.15 K, is acceptable (NIST Table IV).
  watch_out:
    - Sea water. Carpenter rates 304 and 304L restricted in sea water, and no pitting number for 304L was found.
    - Sensitization. Holds between 450 and 900 C form chromium carbide at grain boundaries.
    - Vacuum outgassing. NIST Table IV gives the vacuum-fired 316L-XHV chamber a relative improvement factor of 184 over 304L.
  verdict: 304L is the welded, low-carbon choice of the 18-8 family. Use it where carbide precipitation at a weld would matter. In sea water Carpenter rates it restricted, and Wikipedia says 316 is commonly used in place of 304 where chloride pitting is too severe.