Stainless steel 444 444 (UNS S44400)

spore: profile
id: stainless-444
spore_version: 0.2
family: stainless-ferritic
name: Stainless steel 444
abbreviation: 444 (UNS S44400)
role: corrosion-resistant ferritic sheet, tube and tank alloy
category: metals
type: steels-and-stainless
summary: Type 444 (UNS S44400, EN 1.4521) is a ferritic stainless steel with about 18 percent chromium and 2 percent molybdenum, stabilised with niobium and titanium (ATI, Ugitech). Ugitech says its corrosion resistance is similar to 316L, and ATI reports practical immunity to chloride stress corrosion cracking, where 304 and 316 crack. It is used for hot water tanks, heat exchangers, solar equipment and automotive exhaust parts.
best_for: Hot water tanks, heat exchangers and solar tanks in chloride-bearing water, where resistance to chloride stress cracking matters (ATI, Ugitech, Aperam)
weakest_at: Boiling 10 percent sulphuric and sulfamic acids, where ATI's table shows corrosion above 1000 mils per year, and toughness at transition temperatures, welds included (Aperam)
identity:
  formula: 'Fe balance; 17.5 to 19.5 Cr, 1.75 to 2.50 Mo, max 0.025 C, max 0.035 N (sheet and strip; plate 0.040 to 0.070 N), max 1.00 Si, Mn and Ni, max 0.040 P, max 0.030 S, Nb plus Ti 0.20 + 4(C+N) to 0.80 (wt%, ASTM A240 limits, ATI). Ugitech limits: 17.5 to 19.5 Cr, 1.8 to 2.5 Mo, max 0.025 C, max 0.03 N, max 0.015 S. ATI typical analysis: 18.2 Cr, 1.90 Mo, 0.013 C, 0.015 N. Aperam typical: 17.75 Cr, 1.8 Mo.'
  source: ati-page
  where: Composition table (Sheet) on the ATI product page; Ugitech chemical analysis table; ATI data sheet typical composition; Aperam typical values
  designations:
    - system: UNS
      code: S44400
      source: ati-page
      where: Page heading UNS S44400
    - system: AISI
      code: '444'
      source: aperam-444
      where: Norms list, AISI 444
    - system: EN
      code: '1.4521'
      source: ugi-4521
      where: Designation table, Europe EN column
    - system: EN name
      code: X2CrMoTi18-2
      source: ugi-4521
      where: Designation table, X2CrMoTi18-2 name on the 1.4521 row
    - system: JIS
      code: SUS444
      source: ugi-4521
      where: Designation table, Japan JIS column
    - system: ISO
      code: 4521-444-00-I
      source: outokumpu-global
      where: Table 3, ISO column, 4521 row
    - system: AFNOR
      code: Z3 CDT 18-02
      source: outokumpu-global
      where: Table 3, NF/France column, 4521 row
    - system: SS
      code: '2326'
      source: outokumpu-global
      where: Table 3, SS/Sweden column, 4521 row
    - system: ASTM
      code: A240
      note: plate, sheet and strip
      source: ati-page
      where: Product Specifications for plate, sheet and strip (ASTM A240, ASME SA-240)
    - system: ASME
      code: SA-240
      note: plate, sheet and strip
      source: ati-page
      where: Product Specifications for plate, sheet and strip (ASTM A240, ASME SA-240)
    - system: ASTM
      code: A268
      source: ati-tds
      where: 'Specifications section: UNS S44400 in ASTM A240, A268 and A276'
    - system: ASTM
      code: A276
      source: ati-tds
      where: 'Specifications section: UNS S44400 in ASTM A240, A268 and A276'
    - system: Trade name
      code: ATI 444
      source: ati-page
      where: Page heading ATI 444 Ferritic Stainless Steel
    - system: Trade name
      code: UGI® 4521
      source: ugi-4521
      where: Document title UGI 4521 - UGI 444
    - system: Trade name
      code: UGI® 444
      source: ugi-4521
      where: Document title UGI 4521 - UGI 444
tags:
  environments: []
  stresses:
    - extreme-heat
  applications:
    - thermal-control
    - solar-arrays
    - structures
properties:
  - benchmark: density
    value: 7.75
    unit: g/cm3
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: 22 C (72 F)
    method: Physical properties table, printed as 7.75 g/cm3 (0.280 lb/in3) at 72 F (22 C)
    status: ground
    source: ati-tds
    where: Physical properties table, Density row
  - benchmark: density
    value: 7.7
    unit: g/cm3
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 C
      unit_in_source: kg/dm3 (same unit as g/cm3)
    method: Physical properties table, 20 C row, printed as 7.7 kg/dm3
    status: ground
    source: ugi-4521
    where: Physical properties table, 20 C row, Density column
  - benchmark: specific_heat
    value: 447
    unit: J/kg.K
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: not printed
      unit_in_source: J/Kg•K
    method: Physical properties table, Specific Heat row, printed as 447 J/Kg•K (0.107 BTU/lb/F); no temperature is printed
    status: ground
    source: ati-tds
    where: Physical properties table, Specific Heat row
  - benchmark: specific_heat
    value: 460
    unit: J/kg.K
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 C
    method: Physical properties table, 20 C row, Specific heat column, printed as 460 J/kg.K
    status: ground
    source: ugi-4521
    where: Physical properties table, 20 C row, Specific heat column
  - benchmark: specific_heat
    value: 430
    unit: J/kg°C
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: room temperature (RT column)
    method: Table 12 (physical properties), 4521 row, specific heat capacity c at RT, printed as 430 J/kg°C
    status: ground
    source: outokumpu-global
    where: Table 12, 4521 row, c RT column
  - benchmark: thermal_conductivity
    value: 21.4
    unit: W/m.K
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: 100 C (212 F)
      unit_in_source: W/m•K
    method: Physical properties table, printed as 21.4 W/m•K (12.4 BTU/hr•ft•F) at 212 F (100 C)
    status: ground
    source: ati-tds
    where: Physical properties table, Thermal Conductivity row
  - benchmark: thermal_conductivity
    value: 23
    unit: W/m.K
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 C
      unit_in_source: W/m°C
    method: Physical properties table, 20 C row, Thermal conductivity column, printed as 23 W/m°C
    status: ground
    source: ugi-4521
    where: Physical properties table, 20 C row, Thermal conductivity column
  - benchmark: thermal_conductivity
    value: 24.8
    unit: W/m.K
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 100 C
      unit_in_source: W/m.°C
    method: Physical properties table, 100 C row, Thermal conductivity column, printed as 24.8 W/m.°C
    status: ground
    source: ugi-4521
    where: Physical properties table, 100 C row, Thermal conductivity column
  - benchmark: cte
    value: 10.3
    unit: 10-6/°C
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: 20 to 200 C (68 to 392 F)
      unit_in_source: µ m/m/°C
    method: Physical properties table, Coefficient of expansion row, printed as 10.3 µ m/m/°C (5.7 µ in/in/F) for 68 to 392 F
    status: ground
    source: ati-tds
    where: Physical properties table, Coefficient of expansion row (68 to 392 F)
  - benchmark: cte
    value: 10.4
    unit: 10-6/°C
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 to 100 C
    method: Physical properties table, 100 C row, coefficient of expansion between 20 C and T, printed as 10.4 (10-6/°C)
    status: ground
    source: ugi-4521
    where: Physical properties table, 100 C row, coefficient of expansion column
  - benchmark: cte
    value: 11.6
    unit: 10-6/°C
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 to 400 C
    method: Table 12, 4521 row, coefficient of expansion between 20 C and 400 C, printed as 11.6 (10-6/°C)
    status: ground
    source: outokumpu-global
    where: Table 12, 4521 row, coefficient of expansion 400 C column
  - benchmark: elastic_modulus
    value: 215
    unit: GPa
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 C
    method: Physical properties table, 20 C row, Modulus of elasticity column, printed as 215 GPa
    status: ground
    source: ugi-4521
    where: Physical properties table, 20 C row, Modulus of elasticity column
  - benchmark: elastic_modulus
    value: 220
    unit: GPa
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: room temperature (RT column)
    method: Table 12, 4521 row, modulus of elasticity E at RT, printed as 220 GPa
    status: ground
    source: outokumpu-global
    where: Table 12, 4521 row, E RT column
  - benchmark: elastic_modulus
    value: 195
    unit: GPa
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 400 C
    method: Table 12, 4521 row, modulus of elasticity E at 400 C, printed as 195 GPa
    status: ground
    source: outokumpu-global
    where: Table 12, 4521 row, E 400 C column
  - benchmark: electrical_resistivity
    value: 800
    unit: µΩ.mm
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 20 C
    method: Physical properties table, 20 C row, Electrical resistivity column, printed as 800 µΩ.mm
    status: ground
    source: ugi-4521
    where: Physical properties table, 20 C row, Electrical resistivity column
  - benchmark: electrical_resistivity
    value: 0.8
    unit: μΩm
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: room temperature (RT column)
    method: Table 12, 4521 row, electrical resistivity rho at RT, printed as 0.80 μΩm
    status: ground
    source: outokumpu-global
    where: Table 12, 4521 row, electrical resistivity column
  - benchmark: yield_strength
    value: 345
    unit: MPa
    bound: exact
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: not printed
      basis: 0.2 percent offset, typical
    method: Property table, Yield Strength 0.2% offset, Typical Value column, printed as 345 MPa (50 ksi)
    status: ground
    source: ati-tds
    where: Property table, Typical Value column, Yield Strength row
  - benchmark: yield_strength
    value: 275
    unit: MPa
    bound: lower
    scope: material
    conditions:
      form: sheet, strip and plate (ASTM A240 and ASME SA-240 minimum)
      temper: not printed
      temperature: not printed
      basis: minimum, basis not printed
    method: Product Specifications tables, Yield Strength row, printed as 40 min ksi and 275 min MPa
    status: ground
    source: ati-page
    where: Product Specifications, Sheet table, Yield Strength row
  - benchmark: yield_strength
    value: 300
    unit: MPa
    bound: lower
    scope: material
    conditions:
      form: turned bars (indicative data)
      temper: not printed
      temperature: 20 C
      basis: 0.2 percent offset
    method: Mechanical properties table, 20 C row, Yield strength (0,2%) column, printed as ≥ 300 MPa
    status: ground
    source: ugi-4521
    where: Mechanical properties table, 20 C row, Yield strength column
  - benchmark: yield_strength
    value: 350
    unit: MPa
    bound: exact
    scope: material
    conditions:
      form: cold rolled coil and sheet (typical, product code C)
      temper: not printed
      temperature: room temperature (Table 6)
      basis: Rp0.2, typical
    method: Table 6 (mechanical properties at room temperature), 4521 row, Outokumpu typical values, Rp0.2 column, printed as 350 MPa
    status: ground
    source: outokumpu-global
    where: Table 6, 4521 row, Rp0.2 typical column
  - benchmark: yield_strength
    value: 320
    unit: MPa
    bound: lower
    scope: material
    conditions:
      form: EN minimum, mainly hot rolled plate, transverse direction (Table 6 note)
      temper: not printed
      temperature: room temperature (Table 6)
      basis: Rp0.2 EN minimum
    method: Table 6, 4521 row, EN min values, Rp0.2 column, printed as 320 MPa
    status: ground
    source: outokumpu-global
    where: Table 6, 4521 row, EN min Rp0.2 column
  - benchmark: ultimate_tensile_strength
    value: 517
    unit: MPa
    bound: exact
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: not printed
    method: Property table, Ultimate Tensile Strength, Typical Value column, printed as 517 MPa (75 ksi)
    status: ground
    source: ati-tds
    where: Property table, Typical Value column, Ultimate Tensile Strength row
  - benchmark: ultimate_tensile_strength
    value: 415
    unit: MPa
    bound: lower
    scope: material
    conditions:
      form: sheet, strip and plate (ASTM A240 and ASME SA-240 minimum)
      temper: not printed
      temperature: not printed
    method: Product Specifications tables, Tensile Strength row, printed as 60 min ksi and 415 min MPa
    status: ground
    source: ati-page
    where: Product Specifications, Sheet table, Tensile Strength row
  - benchmark: ultimate_tensile_strength
    value: 450
    value_high: 600
    unit: MPa
    bound: range
    scope: material
    conditions:
      form: turned bars (indicative data)
      temper: not printed
      temperature: 20 C
    method: Mechanical properties table, 20 C row, Tensile strength column, printed as 450 - 600 MPa
    status: ground
    source: ugi-4521
    where: Mechanical properties table, 20 C row, Tensile strength column
  - benchmark: ultimate_tensile_strength
    value: 525
    unit: MPa
    bound: exact
    scope: material
    conditions:
      form: cold rolled coil and sheet (typical, product code C)
      temper: not printed
      temperature: room temperature (Table 6)
    method: Table 6, 4521 row, Outokumpu typical values, Rm column, printed as 525 MPa
    status: ground
    source: outokumpu-global
    where: Table 6, 4521 row, Rm typical column
  - benchmark: ultimate_tensile_strength
    value: 420
    unit: MPa
    bound: lower
    scope: material
    conditions:
      form: EN minimum, mainly hot rolled plate, transverse direction (Table 6 note)
      temper: not printed
      temperature: room temperature (Table 6)
    method: Table 6, 4521 row, EN min values, Rm column, printed as 420 MPa
    status: ground
    source: outokumpu-global
    where: Table 6, 4521 row, EN min Rm column
  - benchmark: elongation
    value: 30
    unit: '%'
    bound: exact
    scope: material
    conditions:
      form: not printed (ATI typical data)
      temper: not printed
      temperature: not printed
      gauge: 2 in (51 mm)
    method: Property table, Elongation in 2 in row, Typical Value column, printed as 30%
    status: ground
    source: ati-tds
    where: Property table, Typical Value column, Elongation in 2 in row
  - benchmark: elongation
    value: 20
    unit: '%'
    bound: lower
    scope: material
    conditions:
      form: sheet, strip and plate (ASTM A240 and ASME SA-240 minimum)
      temper: not printed
      temperature: not printed
      gauge: not printed
    method: Product Specifications tables, Elongation row, printed as 20% min
    status: ground
    source: ati-page
    where: Product Specifications, Sheet table, Elongation row
  - benchmark: elongation
    value: 28
    unit: '%'
    bound: lower
    scope: material
    conditions:
      form: turned bars (indicative data)
      temper: not printed
      temperature: 20 C
      gauge: not printed
    method: Mechanical properties table, 20 C row, Elongation column, printed as ≥ 28
    status: ground
    source: ugi-4521
    where: Mechanical properties table, 20 C row, Elongation column
  - benchmark: hardness
    value: 96
    unit: HRB
    bound: upper
    scope: material
    conditions:
      form: sheet, strip and plate (ASTM A240 and ASME SA-240 maximum)
      temper: not printed
      temperature: not printed
      scale: Rockwell B
    method: Product Specifications tables, Hardness row, printed as 96 HRB max
    status: ground
    source: ati-page
    where: Product Specifications, Sheet table, Hardness row
  - benchmark: max_service_temp
    value: 850
    unit: °C
    bound: upper
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: continuous service in air
    method: General presentation, printed as service temperature can rise to 850°C in air
    status: ground
    source: ugi-4521
    where: General presentation, page 1 of 6
  - benchmark: max_service_temp
    value: 600
    unit: °C
    bound: upper
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: service in the presence of water or sulphur compounds
    method: General presentation, printed as up to 600°C in the presence of water or sulphur compounds
    status: ground
    source: ugi-4521
    where: General presentation, page 1 of 6
  - benchmark: pitting_potential
    value: 0.58
    unit: V vs SCE
    bound: exact
    scope: material
    conditions:
      form: not printed
      temper: not printed
      temperature: 25 C
      solution: 1000 ppm Cl- from NaCl, pH 5
      unit_in_source: Volts vs. Saturated Calomel Electrode
    method: Pitting potential table (cyclic potentiodynamic polarization), AL 444 row, printed as 0.58 Volts vs. Saturated Calomel Electrode; a more positive potential means more resistance to initiating localized chloride attack
    status: ground
    source: ati-tds
    where: Pitting and Crevice Corrosion section, pitting potential table, AL 444 row
corrosion:
  - environment: Chloride stress corrosion cracking in boiling salt solutions (42% MgCl2, 33% LiCl, 26% NaCl)
    headline: ATI 444 passed in all three boiling chloride solutions over 1000 hours, while ATI 304 and ATI 316 cracked in all three.
    effect: ATI tested U-bend specimens to ASTM G30 in boiling 42% MgCl2, 33% LiCl and 26% NaCl for 1000 hours. Alloy 444 showed no cracking, while ATI 304 and ATI 316 cracked in every solution. ATI calls 444 practically immune to chloride stress corrosion cracking and names this as one big advantage over austenitic grades.
    rating: low
    conditions:
      exposure: boiling, 1000 hours, U-bend specimens (ASTM G30)
    source: ati-tds
    where: Stress Corrosion Cracking Resistance section and its table
  - environment: Chloride stress corrosion cracking, producer data in boiling salts (SSINA)
    headline: SSINA's producer data show 444 with no cracking in boiling 26% NaCl, 33% LiCl and 42% MgCl2, against cracking of 304L and 316L in all three.
    effect: SSINA says the ferritic family, which includes 444, is very resistant to chloride SCC, while 304/304L and 316/316L are very susceptible. Its table shows 444 with no cracking in the three boiling salts (fully immersed U-bend specimens, producer data). SSINA adds that no stainless steel grade is totally immune, and that evaporation on hot surfaces can cause cracking well below the immersion thresholds.
    rating: low
    source: ssina-scc
    where: Corrosion Testing section, Table 1 (relative chloride SCC resistance)
  - environment: Stress corrosion cracking, general statement (Ugitech)
    headline: Ugitech says the ferritic structure makes 4521 insensitive to stress corrosion, which suits pressure use.
    effect: Ugitech says 4521 is insensitive to stress corrosion because of its ferritic structure, which makes it suitable for use under pressure, and that this mode of corrosion can be a weak point of certain austenitic grades.
    rating: low
    source: ugi-4521
    where: Resistance to corrosion, Stress corrosion paragraph (page 3 of 6)
  - environment: Chloride pitting potential in 1000 ppm chloride (NaCl, pH 5, 25 C)
    headline: ATI gives 444 a pitting potential of 0.58 V vs SCE, above 304 (0.35) and 316 (0.56).
    effect: ATI's cyclic polarization test gives 444 a more positive pitting potential than 304 or 316. A more positive potential means more resistance to initiating localized chloride attack. The test uses 1000 ppm chloride from NaCl at pH 5 and 25 C.
    rating: low
    source: ati-tds
    where: Pitting and Crevice Corrosion section, pitting potential table
  - environment: Pitting in environments from drinking water to brines more concentrated than seawater (23 to 35 C)
    headline: Ugitech says pitting resistance is better than 316L (1.4404) across that range, and prints a PREN of 24,5.
    effect: Ugitech says the pitting resistance of UGI 4521 is better than that of type 316L/1.4404 and UGI 4404 from 23 C to 35 C, in environments from drinking water to brines more concentrated than seawater. Its pitting potential is higher than that of UGI 4404 over a wide range of chloride concentrations. Ugitech's PREN (%Cr + 3.3%Mo + 16%N) is printed as 24,5 and is said to sit above 304L/1.4307 and 316L/1.4404.
    rating: low
    source: ugi-4521
    where: Resistance to corrosion, Pitting corrosion paragraph (pages 2 and 3 of 6)
  - environment: Crevice (cavernous) corrosion in complex geometry
    headline: Ugitech says crevice corrosion can be a weak point of ferritic grades, but 4521 is equivalent to 316L (1.4404) in most applications.
    effect: Ugitech says cavernous corrosion can be a weak point of ferritic grades. Because of its composition, UGI 4521 has a resistance equivalent to that of UGI 4404 in most applications. For critical cases with complex geometry and confined retention zones, Ugitech asks users to consult it.
    rating: moderate
    source: ugi-4521
    where: Resistance to corrosion, Cavernous corrosion paragraph (page 3 of 6)
  - environment: Intergranular corrosion (ASTM A262 Practice E)
    headline: ATI reports no intergranular attack after the Cu-CuSO4-16% H2SO4 test, and no post-weld heat treatment is needed.
    effect: ATI reports no evidence of intergranular corrosion after the Cu-CuSO4-16% H2SO4 test (ASTM A262 Practice E). The titanium plus niobium content must be 0.20 + 4(C+N) minimum and 0.80 maximum. No post-weld heat treatment is required to restore corrosion performance.
    rating: low
    source: ati-tds
    where: Intergranular Corrosion Resistance section
  - environment: Intergranular corrosion in the delivery and welded conditions
    headline: Outokumpu prints Y/Y (yes in both conditions) for 4521 under intergranular corrosion resistance.
    effect: Outokumpu's fabrication table prints Y/Y for 4521 under intergranular corrosion resistance, with footnote 6 saying the test follows EN 10088-2 and EN ISO 3651-2 for the delivery and welded conditions. Ugitech says the grade resists intergranular corrosion well (ASTM A763-14).
    rating: low
    source: outokumpu-global
    where: Table 14, 4521 row, IGC resistance column, footnote 6
  - environment: Boiling 1% hydrochloric acid and 20% phosphoric acid
    headline: In boiling 1% hydrochloric acid 444 corroded at 1.7 mils per year, against 88.3 for 304 and 226 for 316.
    effect: 'ATI''s boiling-solution table, average of five 48-hour periods, gives 444 at 1.7 mils per year in 1% HCl (304: 88.3; 316: 226) and at 2.3 in 20% phosphoric acid (304: 2.6; 316: 0.2). In 20% acetic acid 444 gave 0.1, against 0.12 for 304 and below 0.1 for 316.'
    rating: low
    conditions:
      unit_in_source: mils per year
      exposure: boiling, average of five 48-hour periods
    source: ati-tds
    where: Corrosion Resistance section, General Corrosion Resistance table (boiling solutions)
  - environment: Boiling 10% sulfuric acid and 10% sulfamic acid
    headline: 444 corroded above 1000 mils per year in both boiling acids, the most severe result for 444 in ATI's table.
    effect: 'ATI gives more than 1000 mils per year for 444 in boiling 10% sulfuric acid (304: 446; 316: 636) and in boiling 10% sulfamic acid (304: 127; 316: 83.4).'
    rating: severe
    conditions:
      unit_in_source: mils per year
      exposure: boiling, average of five 48-hour periods
    source: ati-tds
    where: General Corrosion Resistance table, 10% Sulfuric Acid and 10% Sulfamic Acid rows
  - environment: Boiling 65% nitric acid, 10% oxalic acid and 50% sodium hydroxide
    headline: 444 is worse than 304 in boiling 65% nitric acid (18 against 8.4 mils per year) and in 50% sodium hydroxide (293 against 183 for 304 and 123 for 316).
    effect: ATI's table also shows 444 at 18 mils per year in boiling 65% nitric acid, against 8.4 for 304 and 41.3 for 316, and at 293 in boiling 50% sodium hydroxide. In boiling 10% oxalic acid 444 gave 101, against 46.5 for 304 and 51.4 for 316.
    rating: moderate
    conditions:
      unit_in_source: mils per year
      exposure: boiling, average of five 48-hour periods
    source: ati-tds
    where: General Corrosion Resistance table, 65% Nitric Acid, 10% Oxalic Acid and 50% Sodium Hydroxide rows
  - environment: Chloride media (pitting), Aperam South America offer
    headline: Aperam says 444 has very good pitting resistance in chloride media, outperforming 304L and 316L.
    effect: Aperam lists 444 with very good resistance to pitting corrosion in chloride media, outperforming 304L (18-9L) and 316L (18-11ML). Aperam also says the grade is not sensitive to stress cracking or intergranular corrosion.
    rating: low
    source: aperam-444
    where: Main features
  - environment: High-temperature service in air, water or sulphur compounds
    headline: Ugitech gives a service temperature up to 850°C in air and 600°C in the presence of water or sulphur compounds.
    effect: Ugitech says the grade keeps good mechanical properties at high temperature and that its service temperature can rise to 850°C in air and go up to 600°C in the presence of water or sulphur compounds.
    rating: low
    source: ugi-4521
    where: General presentation, page 1 of 6
risks:
  hazards:
    - text: PubChem's aggregated GHS notifications for elemental chromium (CID 23976) include H317 (20.7 percent of notifications), H319 (19.1 percent) and H334 (20.3 percent, signal word Danger). H335 also appears. The record is for chromium, not for the 444 alloy.
      ghs:
        - H317
        - H319
        - H334
        - H335
      source: pubchem-cr
      where: Hazards Identification, GHS Classification (PubChem CID 23976)
    - text: PubChem reports that 1202 of 2404 company reports say elemental chromium does not meet GHS hazard criteria.
      ghs: []
      source: pubchem-cr
      where: Hazards Identification, ECHA C&L Notifications Summary (PubChem CID 23976)
  failure_risks:
    - mode: Low toughness at transition temperatures, including in welded zones
      trigger: Service near the transition temperature range
      consequence: Aperam says the grade has low toughness at transition temperatures, even in welded zones.
      severity: moderate
      source: aperam-444
      where: Main features
    - mode: Coarse grain and loss of toughness in thick welds
      trigger: Welding, and any heat treatment before or after welding
      consequence: Ugitech says no heat treatment should be done before or after welding, to avoid coarsening the ferritic grain. For thick welds (3 mm or more) it recommends an austenitic filler, to avoid embrittlement of the weld zone by excessive grain size.
      severity: moderate
      source: ugi-4521
      where: Welding section, page 6 of 6
    - mode: Crevice corrosion in complex geometry
      trigger: Parts with confined retention zones
      consequence: Ugitech says cavernous corrosion can be a weak point of ferritic grades, and asks users to consult it for critical cases.
      severity: moderate
      source: ugi-4521
      where: Resistance to corrosion, Cavernous corrosion paragraph (page 3 of 6)
    - mode: Fast attack in boiling sulfuric and sulfamic acid
      trigger: Boiling 10% sulfuric acid or boiling 10% sulfamic acid
      consequence: ATI's boiling test gives more than 1000 mils per year for 444 in both acids.
      severity: high
      source: ati-tds
      where: General Corrosion Resistance table, sulfuric and sulfamic acid rows
  side_effects: []
  handling:
    - text: Ugitech says to restore ductility after cold forming, treat 4521 at 750 to 900°C and cool in air.
      source: ugi-4521
      where: Thermal Treatment, Softening (page 6 of 6)
    - text: Outokumpu's heat treatment column prints 850 ± 30 C for 4521 (A = annealing).
      source: outokumpu-global
      where: Table 14, 4521 row, heat treatment temperature column
    - text: Use gas-shielded welding processes. ATI prefers argon shielding and says the shielding gas must not contain hydrogen or nitrogen, and that procedures should minimise the pick-up of oxygen, carbon and nitrogen.
      source: ati-tds
      where: Weldability section
    - text: Ugitech says no heat treatment should be done before or after welding.
      source: ugi-4521
      where: Welding section, page 6 of 6
    - text: Weld colour can be removed by mechanical or chemical pickling with 10% HNO3 + 2% HF, then depassivate in a cold nitric bath at 20 to 25 C (Ugitech).
      source: ugi-4521
      where: Surface treatment, page 6 of 6
    - text: Hot form 4521 between 800 and 1250°C and avoid heating above 1150°C, to limit grain size (Ugitech).
      source: ugi-4521
      where: Hot processing, page 4 of 6
  mitigations:
    - text: Use an austenitic filler such as ER308L(Si) (1.4316) for thick welds (3 mm or more), to avoid embrittlement from excessive grain size in the weld zone (Ugitech).
      source: ugi-4521
      where: Welding section, page 6 of 6
    - text: Use a stabilised ferritic filler such as EXHAUST F1 (18LNb) so the weld zone stays fully ferritic (Ugitech).
      source: ugi-4521
      where: Welding section, page 6 of 6
    - text: Use argon shielding without hydrogen or nitrogen, and gas-shielded processes, to keep weld corrosion resistance and ductility (ATI).
      source: ati-tds
      where: Weldability section
uses:
  - application: thermal-control
    device: Heat exchanger tubing, boilers and hot water tanks
    example: ATI lists heat exchanger tubing and hot water tanks as common applications. Ugitech lists boilers and heat exchangers, and Aperam lists hot water tanks, boilers, heat exchangers and solar tanks.
    source: ati-tds
    where: Introduction; Ugitech Applications list (page 6 of 6); Aperam Applications list
  - application: solar-arrays
    device: Photovoltaic frames and solar panels
    example: Aperam lists photovoltaic frames and solar panels among its applications. Ugitech names solar panels among its high-temperature uses.
    source: aperam-444
    where: Applications list
  - application: structures
    device: Automotive exhaust systems
    example: ATI says its resistance to hot corrosion and good creep resistance make 444 an excellent choice for automotive exhaust applications.
    source: ati-tds
    where: Introduction
  - application: structures
    device: Water tanks, fume ducts, sanitary tubes and cooking equipment
    example: Aperam lists water tanks, fume ducts, sugar and sanitary tubes, and cooking and catering equipment among its applications. ATI lists food processing equipment.
    source: aperam-444
    where: Applications list
  - application: structures
    device: Pressure equipment under EN and ASME pressure-purpose listings
    example: Outokumpu lists 4521 as a pressure-purpose grade under EN and ASME. Ugitech says it is suitable for use under pressure.
    source: outokumpu-global
    where: Table 14, 4521 row, pressure purpose column
supply:
  - subject: Chromium
    abundance: World mine production 51,000 thousand metric tons gross weight in 2025e (49,600 in 2024). World resources are greater than 12 billion tons of shipping-grade chromite, 95 percent 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
      - country: Finland
        share_percent: 3.7
        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-cr-2026
    where: World Mine Production and Reserves table (2025e; shares computed from the printed tonnages); World Resources; Recycling; Substitutes
  - subject: Chromium import reliance (United States)
    abundance: 'US net import reliance 79 percent of apparent consumption in 2025e (76 in 2021). Chromite imports 2021 to 2024: South Africa 96 percent, Turkey 3 percent, other 1 percent (USGS 2026).'
    producers: []
    critical_lists: []
    substitutes: []
    source: usgs-cr-2026
    where: Salient Statistics (net import reliance row); Import Sources (2021 to 2024)
  - subject: Molybdenum
    abundance: World mine production 260,000 metric tons of molybdenum content in 2025e (256,000 in 2024). China, Chile, the United States, Peru and Mexico produced 90 percent of world output in 2025. China imposed export controls on molybdenum powders in February 2025 (USGS 2026).
    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 recycled as part of new and old steel and other scrap may be as much as 30 percent of apparent supply (USGS 2026)
    substitutes:
      - Little substitution for molybdenum in steels and cast irons; potential substitutes are boron, chromium, niobium and vanadium in alloy steels (USGS 2026)
    source: usgs-mo-2026
    where: World Mine Production and Reserves table (2025e; shares computed from the printed tonnages); Events, Trends, and Issues; Recycling; Substitutes
  - subject: Molybdenum import reliance (United States)
    abundance: 'The United States is a net exporter of molybdenum (E in the net import reliance row, 2021 to 2025e). Total imports 2021 to 2024: Chile 36 percent, Peru 35 percent, Mexico 8 percent, Republic of Korea 7 percent, other 14 percent (USGS 2026).'
    producers: []
    critical_lists: []
    substitutes: []
    source: usgs-mo-2026
    where: Salient Statistics (net import reliance row, footnote E); Import Sources (2021 to 2024)
media: []
documents:
  - title: ATI 444 Technical Data Sheet (Ferritic Stainless Steel, UNS S44400), version 1
    type: datasheet
    url: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/ferritic/ati_444_tds_en_v1.pdf
    year: 2014
  - title: ATI 444 Ferritic Stainless Steel product page (composition, ASTM A240 and ASME SA-240 product specifications)
    type: datasheet
    url: https://www.atimaterials.com/Products/ati-444
  - title: 'Ugitech (Swiss Steel Group): Technical notice UGI 4521 - UGI 444 (1.4521, X2CrMoTi18-2, S44400), REV 01'
    type: datasheet
    url: https://swisssteel-group.com/content-media/documents/_import/DAT-UGI-4521-en.pdf
    year: 2022
  - title: 'Aperam: 444 - UNS S44400 product page (South America offer, norms and typical chemical composition)'
    type: datasheet
    url: https://www.aperam.com/product/444-s44400/
  - title: 'Outokumpu: Steel Grades, Properties and Global Standards (Tables 2, 3, 6, 12 and 14)'
    type: datasheet
    url: https://www.outokumpu.com/-/media/from-sharepoint/documents/product/outokumpu-steel-grades-properties-global-standards.pdf
  - title: 'SSINA: Chloride Stress Corrosion Cracking (Table 1, relative chloride SCC resistance)'
    type: report
    url: https://www.ssina.com/education/corrosion/chloride-stress-corrosion-cracking/
  - 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: Chromium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
  - title: 'PubChem: Chromium (CID 23976), UN GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23976/JSON
gaps:
  - No melting point or melting range is printed in the sources read in this run.
  - No Poisson's ratio, shear or bulk modulus, or fatigue strength is printed in the sources read.
  - 'No Charpy impact value is recorded: Outokumpu''s KV column is blank for 4521, and Aperam''s transition-temperature toughness statement is qualitative.'
  - 'PREN: Ugitech prints 24,5 with a decimal comma. The gate reads a comma as a thousands separator, so the PREN stays in the corrosion text and is not a property.'
  - The pitting_potential and hardness benchmarks are not in spores/property-canon.yaml, so they use short snake_case names. Hardness is in HRB as printed.
  - Ugitech prints ISO 4421-444-00-I and Outokumpu prints 4521-444-00-I. The Outokumpu code is recorded.
  - The ATI data sheet prints ASTM A249 as the column heading for its minimum values. The minima used here come from the ATI product page under ASTM A240 and ASME SA-240.
  - Ulbrich and the Cleveland-Cliffs ASM Alloy Digest could not be opened (a Cloudflare block and a JavaScript page), so no values are taken from them.
  - No safety data sheet for 444 was read. The hazard entries rest on PubChem's record for elemental chromium, and welding-fume hazards for 444 are not sourced.
  - Critical-mineral status is not printed in the USGS 2026 chromium or molybdenum texts read, so critical_lists is empty.
  - The Outokumpu catalogue prints no edition year, so its source has no year.
  - 'Service temperature differs by source: Ugitech gives 850°C in air and 600°C with water or sulphur compounds. ATI''s ASME Section VIII Division 1 listing to 650 F is a code limit and is not recorded as a service limit.'
  - Electrical resistivity is printed in µΩ.mm (Ugitech, 800) and in μΩm (Outokumpu, 0.80). Both are recorded as printed.
  - Density is printed in kg/dm3 by Ugitech. It is recorded as g/cm3, with the printed unit kept in conditions; the two units are the same.
  - The chloride pitting critical temperature column in Outokumpu Table 14 prints '< 10' for every ferritic grade, which is ambiguous, so it is not recorded.
  - The ATI crevice-corrosion table (ASTM G48 Practice B, sodium hypochlorite) has duplicate rows that could not be read reliably, so it is not transcribed.
  - No atmospheric-exposure data for 444 were found in the sources read.
  - No NASA, ESA or other space-use source was found. Web search was unavailable after five searches in this run, so no SDS, paper or space-agency source was added.
  - 'Plate chemistry differs from sheet and strip: ATI gives 0.040 to 0.070 N for plate and 0.035 maximum for sheet and strip. Both are recorded in the composition.'
  - Chromium and molybdenum producer shares are computed from the printed 2025e tonnages (USGS 2026), as in the stainless-430 profile.
  - Ugitech's sulphur limit (0.015 maximum) differs from the ASTM A240 limit (0.030 maximum). Both are recorded.
  - The 304 and 316 numbers in the corrosion section are comparison values from the same ATI tables, not properties of 444.
sources:
  ati-tds:
    title: ATI 444 Technical Data Sheet (Ferritic Stainless Steel, UNS S44400), version 1
    id: ati_444_tds_en_v1.pdf
    url: https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/ferritic/ati_444_tds_en_v1.pdf
    kind: datasheet
    year: 2014
    license: cited, not reproduced
  ati-page:
    title: ATI 444 Ferritic Stainless Steel product page (composition, ASTM A240 and ASME SA-240 product specifications)
    id: ati-444
    url: https://www.atimaterials.com/Products/ati-444
    kind: datasheet
    license: cited, not reproduced
  ugi-4521:
    title: 'Ugitech (Swiss Steel Group): Technical notice UGI 4521 - UGI 444, REV 01'
    id: DAT-UGI-4521-en.pdf
    url: https://swisssteel-group.com/content-media/documents/_import/DAT-UGI-4521-en.pdf
    kind: datasheet
    year: 2022
    license: cited, not reproduced
  aperam-444:
    title: 'Aperam: 444 - UNS S44400 product page (South America offer)'
    id: 444-s44400
    url: https://www.aperam.com/product/444-s44400/
    kind: datasheet
    license: cited, not reproduced
  outokumpu-global:
    title: 'Outokumpu: Steel Grades, Properties and Global Standards'
    id: outokumpu-steel-grades-properties-global-standards.pdf
    url: https://www.outokumpu.com/-/media/from-sharepoint/documents/product/outokumpu-steel-grades-properties-global-standards.pdf
    kind: handbook
    license: cited, not reproduced
  ssina-scc:
    title: 'SSINA: Chloride Stress Corrosion Cracking'
    id: chloride-stress-corrosion-cracking
    url: https://www.ssina.com/education/corrosion/chloride-stress-corrosion-cracking/
    kind: web
    license: cited, not reproduced
  usgs-mo-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-cr-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
  pubchem-cr:
    title: 'PubChem: Chromium (CID 23976), UN 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)
license: CC-BY-4.0
updated: '2026-10-24'
review:
  status: draft
  method: assistant
  checked_values: 33
  unreachable: 2
  caveats: 6
  note: 'Read by an AI assistant on 2026-10-24 from pages fetched in this run: ATI 444 data sheet (version 1, 2014) and ATI 444 product page, Ugitech UGI 4521 technical notice (REV 01, 2022), Aperam 444 product page, Outokumpu Steel Grades, Properties and Global Standards (PDF), SSINA chloride SCC page, USGS Mineral Commodity Summaries 2026 for molybdenum and chromium, and PubChem chromium record. Caveats: typical and minimum values differ by product form; Ugitech and Outokumpu give different ISO codes; the PREN is printed with a decimal comma; two sites could not be opened.'
story:
  recipe:
    line: Type 444 is an iron-chromium-molybdenum steel. ASTM A240 limits (ATI product page) give 17.5 to 19.5 percent chromium and 1.75 to 2.50 percent molybdenum, with carbon at 0.025 percent maximum and nitrogen at 0.035 percent maximum for sheet and strip. Ugitech gives 1.8 to 2.5 percent molybdenum. Niobium and titanium are added as stabilisers. It is sold as sheet, plate and strip (ATI), as bars and wire rod (Ugitech), and as coils, sheets and tubes (Aperam).
    parts:
      - name: Iron
        symbol: Fe
        share_note: balance
        role: Main element. ATI describes the alloy as single-phase ferritic (body-centred cubic) at all temperatures up to melting.
        source: ati-tds
        where: Composition table (Iron, balance); Physical Properties introduction
      - name: Chromium
        symbol: Cr
        share_percent: 17.5
        share_high: 19.5
        role: Forms the passive film that gives general corrosion resistance. ATI's typical analysis is 18.2 percent.
        source: ati-page
        where: Composition table, Sheet
      - name: Molybdenum
        symbol: Mo
        share_percent: 1.75
        share_high: 2.5
        role: Raises resistance to pitting and crevice attack in chloride solutions (ATI). ATI's typical analysis is 1.90 percent.
        source: ati-page
        where: Composition table, Sheet
      - name: Carbon
        symbol: C
        share_percent: 0
        share_high: 0.025
        role: Held low, at 0.025 percent maximum. ATI says low carbon and nitrogen, with titanium and niobium stabilisers, give resistance to intergranular corrosion.
        source: ati-page
        where: Composition table, Sheet (C maximum)
      - name: Nitrogen
        symbol: 'N'
        share_percent: 0
        share_high: 0.035
        share_note: 0.035 maximum for sheet and strip; 0.040 to 0.070 for plate (ATI)
        role: Held low. ATI uses a higher nitrogen content in plate to meet ASTM A240 mechanical limits.
        source: ati-page
        where: Composition table, Plate and Sheet; plate note
      - name: Silicon
        symbol: Si
        share_percent: 0
        share_high: 1
        role: Held to 1.00 percent maximum (ASTM A240 limit).
        source: ati-page
        where: Composition table, Sheet
      - name: Manganese
        symbol: Mn
        share_percent: 0
        share_high: 1
        role: Held to 1.00 percent maximum (ASTM A240 limit).
        source: ati-page
        where: Composition table, Sheet
      - name: Nickel
        symbol: Ni
        share_percent: 0
        share_high: 1
        role: Held to 1.00 percent maximum. Ugitech says the low nickel content makes the grade less expensive than 316L-type steels.
        source: ugi-4521
        where: Chemical analysis table (Ni shown as -); General presentation
      - name: Phosphorus
        symbol: P
        share_percent: 0
        share_high: 0.04
        role: Impurity held to 0.040 percent maximum.
        source: ati-page
        where: Composition table, Sheet
      - name: Sulfur
        symbol: S
        share_percent: 0
        share_high: 0.03
        role: Impurity held to 0.030 percent maximum (ATI). Ugitech gives 0.015 percent maximum.
        source: ati-page
        where: Composition table, Sheet
      - name: Niobium plus titanium
        symbol: Nb+Ti
        share_note: 0.20 + 4(C+N) minimum to 0.80 maximum (ATI)
        role: Stabilisers that tie up carbon and nitrogen, so the alloy resists intergranular corrosion, including in welds (ATI, Ugitech).
        source: ati-page
        where: Composition table, (Ti+Cb) row
  risk_groups:
    - title: For people
      level: 1
      verdict: Chromium record, not the alloy
      lead: No safety data sheet for 444 was read in this run. The PubChem record for elemental chromium lists sensitisation and eye-irritation codes, not codes for the alloy.
      points:
        - label: Chromium
          line: PubChem lists H317 and H334 (sensitisation) and H319 (eye irritation) for elemental chromium in its aggregated notifications. 1202 of 2404 reports say it does not meet GHS criteria.
    - title: In the environment
      level: 2
      verdict: Acids and hot alkali set the limit
      lead: Chloride cracking is not the limit for 444. Its weak points are boiling sulphuric and sulfamic acids, and boiling sodium hydroxide, where it corrodes faster than 304 or 316.
      points:
        - label: Sulphuric and sulfamic acid
          line: ATI gives more than 1000 mils per year for 444 in each boiling 10 percent acid, against 446 and 636 for 304 and 316 in sulfuric acid.
        - label: Chloride cracking
          line: ATI reports no cracking in 42% MgCl2, 33% LiCl or 26% NaCl after 1000 hours, while 304 and 316 cracked in all three.
    - title: Welding and heat
      level: 3
      verdict: Heat history sets the risk
      lead: Welds lose toughness when the grain grows, and Aperam says the grade has low toughness at transition temperatures, even in welded zones.
      points:
        - label: Weld
          line: Ugitech says no heat treatment should be done before or after welding, to avoid coarse grain, and recommends an austenitic filler for welds 3 mm or thicker.
        - label: Toughness
          line: Aperam says low toughness at transition temperatures applies even in welded zones.
    - title: Crevices and pitting
      level: 2
      verdict: Pitting is good; crevices need care
      lead: Ugitech says pitting resistance is better than 316L, but crevice corrosion can be a weak point of ferritic grades in complex geometry.
      points:
        - label: Crevice
          line: Ugitech says UGI 4521 is equivalent to 316L in most applications and asks users to consult it for critical crevice cases.
  why: Type 444 is a ferritic chromium-molybdenum steel with about 18 percent chromium and 2 percent molybdenum. Ugitech says its corrosion resistance is similar to the 316L family, and ATI reports practical immunity to chloride stress corrosion cracking, where 304 and 316 crack. It is less expensive than 316L-type steels because it has little or no nickel (Ugitech). Its main listed uses are heat exchangers, hot water tanks and solar equipment (ATI, Ugitech, Aperam).
  uses:
    - where: Heat exchangers, boilers and hot water tanks
      line: ATI and Ugitech both list these uses. Aperam adds solar tanks.
    - where: Solar panels and photovoltaic frames
      line: Aperam lists photovoltaic frames and solar panels. Ugitech lists solar panels among its high-temperature uses.
    - where: Automotive exhaust systems
      line: ATI says its hot corrosion resistance and creep resistance make it an excellent choice for automotive exhaust applications.
    - where: Water tanks, fume ducts and food equipment
      line: Aperam lists water tanks, fume ducts, sanitary tubes and cooking equipment. ATI lists food processing equipment.
  can_do:
    - label: Chloride cracking
      line: No cracking after 1000 hours in boiling 42% MgCl2, 33% LiCl or 26% NaCl, where 304 and 316 cracked (ATI).
    - label: Pitting
      line: Pitting potential of 0.58 V vs SCE in 1000 ppm chloride, above 304 (0.35) and 316 (0.56) in ATI's test.
    - label: Strength
      line: ASTM A240 minimums are 275 MPa yield and 415 MPa tensile for sheet, strip and plate (ATI). Ugitech gives 450 to 600 MPa tensile on turned bars.
    - label: Heat
      line: Ugitech gives a service temperature of up to 850°C in air and 600°C with water or sulphur compounds.
    - label: Forming and welding
      line: Ugitech says it cold forms well by bending, drawing and stretching, and that most arc welding processes can join it.
  compare: 'Against 304 and 316, 444 resists chloride stress corrosion cracking in ATI''s boiling-salt tests, where both austenitic grades crack, and its pitting potential is higher (0.58 V against 0.35 and 0.56 V in ATI''s test). ATI says it conducts heat better and expands less than 304 and 316. It is weaker in several hot acids: in boiling 10% sulfuric acid it gave more than 1000 mils per year, against 446 for 304 and 636 for 316. Ugitech says its yield strength is better than that of the austenitic grades.'
  compare_rows:
    - label: Yield strength
      benchmark: yield_strength
    - label: Ultimate tensile strength
      benchmark: ultimate_tensile_strength
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Anneal at 750 to 900°C and cool in air to restore ductility after cold forming (Ugitech). Outokumpu prints 850 ± 30 C for annealing.
    - Weld with argon shielding and no hydrogen or nitrogen in the gas, and do not heat treat before or after welding (ATI, Ugitech).
    - Remove weld colour with 10% HNO3 + 2% HF, then depassivate in cold nitric acid at 20 to 25 C (Ugitech).
    - Keep hot working below 1150°C to avoid excessive grain size (Ugitech).
  good_for:
    - Hot water tanks, heat exchangers and boilers in chloride-bearing water (ATI, Ugitech, Aperam).
    - Solar panel frames and solar tanks (Aperam, Ugitech).
    - Automotive exhaust parts, where hot corrosion resistance and creep resistance matter (ATI).
    - Parts that need good drawability and weldability (Aperam).
  watch_out:
    - Boiling sulphuric and sulfamic acids, and boiling sodium hydroxide, where 444 corrodes faster than 304 or 316 (ATI).
    - 'Welds and heat history: no heat treatment before or after welding, and an austenitic filler for thick welds (Ugitech). Toughness is low at transition temperatures, welds included (Aperam).'
    - Crevices in complex geometry, where Ugitech asks for a specific review (Ugitech).
  verdict: Type 444 is the chloride-tolerant ferritic grade. It resists chloride stress cracking where 304 and 316 fail, and its corrosion resistance is similar to 316L (Ugitech). It is weaker in boiling sulphuric and sulfamic acids, its toughness is low at transition temperatures (Aperam), and it needs careful welding.