444 Stainless Steel (UNS S44400, SUS444, 1.4521 / X2CrMoTi18-2)

444 is a ferritic stainless steel containing approximately 18% chromium and 2% molybdenum, with very low carbon and nitrogen content. The molybdenum addition gives 444 outstanding resistance to pitting corrosion and stress corrosion cracking — significantly better than 430 and comparable to 316L in many chloride environments.

Key Features

• Excellent pitting and crevice corrosion resistance in chloride media
• Superior stress corrosion cracking resistance versus austenitic grades
• Good thermal conductivity and low thermal expansion
• Attractive 2B, BA and polished surface finishes

Specifications

Custom sizes, surface finishes and coil/sheet forms can be produced to your requirements. Please contact us for the latest price and free samples.

Category: Ferritic stainless steel, ultra-low carbon & nitrogen, stabilized with Ti/Nb, 18Cr‑2Mo gradeATI

Chinese equivalent: S11972 (019Cr19Mo2NbTi)

1. Chemical Composition (wt%, ASTM A240 / UNS S44400)

Notes:

• Ultra-low C & N prevent intergranular corrosion after welding.
• Molybdenum greatly improves resistance to pitting & crevice corrosion in chloride environments.
• Ti/Nb stabilisation binds residual carbon and nitrogen, avoiding weld sensitizationATI.

2. Mechanical Properties (Annealed condition, room temperature, minimum values ASTM A240)

Physical & Metallurgical Properties

• Density: ~7.70 g/cm³
• Elastic Modulus: ~200 GPa
• Thermal conductivity: ~26.8 W/(m·K) (higher than 304/316 austenitic stainless steel)
• Coefficient of thermal expansion: ~10.5 ×10⁻⁶ /K (lower than austenitic grades)
• Magnetic: Ferromagnetic
• Not heat-treatable for hardening; strength can only be increased by cold working
• Excellent resistance to chloride stress corrosion cracking (SCC) (big advantage over 304 / 316L)ATI

3. Corrosion Characteristics

1. Good resistance to pitting, crevice corrosion in hot water and low-to-moderate chloride media.
2. Virtually immune to chloride stress corrosion cracking, which is a common failure mode for 304/316L in hot chlorinated water.
3. Stabilized chemistry → no intergranular corrosion after welding, no post-weld annealing required.
4. Not suitable for strong oxidizing acids (e.g. concentrated nitric acid).

4. Applications

• Water heater tanks, hot water storage vessels, geysers (the most typical application for 444)
• Heat exchanger tubes, evaporators for water, steam & mild brine service
• Food & beverage processing equipment: brewery, wine, dairy machinery (FDA / NSF compliant)
• Solar thermal water system components
• Automotive exhaust parts
• Marine atmosphere architectural cladding, roofing (low chloride marine environment)
• Water treatment equipment, desalination pre-treatment components
• Sanitary piping for hot potable water systems

5. Fabrication Notes

• Weldable by GTAW (TIG), GMAW; matching ferritic filler metals recommended.
• Formability is moderate; better than high-alloy ferritic stainless steel, inferior to 304.
• Avoid long time exposure at 400–500°C (475°C embrittlement risk for ferritic stainless steel).
• Cost advantage: No expensive nickel, so generally cheaper than 316L for hot water & chloride SCC service.