X2CrMoTi18-2 / 1.4521 / S44400 / SUS444 Mo-Bearing Ferritic Stainless Steel (AISI 444) — FUSHUN METAL

In many chloride-bearing environments — yes, with significant advantages. 444 matches 316L’s PREN (~26), making it equivalent in pitting resistance. It outperforms 316L in stress-corrosion cracking (SCC) immunity: 316L can fail catastrophically by SCC above ~60°C in chloride solutions, while 444’s nickel-free ferritic structure is inherently immune. Additionally, 444’s thermal conductivity is ~75% higher and thermal expansion ~40% lower — beneficial in heat-exchanger and cyclic-temperature service. Limits: 444 is not suitable for cryogenic service (toughness drops below -20°C), not recommended for strong reducing acids (HCl, HF), and has lower formability in deep-drawing compared to austenitic 316L. For welded pressure vessels per PED 2014/68/EU, 444 is fully approved.

Molybdenum enriches the passive chromium-oxide film, forming a mixed Cr-Mo oxyhydroxide layer that is far more resistant to chloride-ion breakdown than a pure Cr₂O₃ film. In practical terms: in a 3.5% NaCl solution at 50°C, the pitting potential of 444 shifts positively by ~400 mV compared to Mo-free 439. This means chlorides that would initiate pits on 439 or 304 simply cannot penetrate the passive film on 444. Mo is also soluble in the ferrite matrix up to ~2.5%, so it does not form brittle secondary phases — provided the grade is properly annealed and cooled through the 475°C embrittlement range rapidly.

Yes — and it welds better than most ferritic grades thanks to Ti stabilization. Use TIG or MIG with ER444 or ER316L filler; pure argon shielding. Unlike unstabilized grades, post-weld annealing is generally not required because Ti binds free carbon/nitrogen, preventing sensitization in the HAZ. However, for heavy-gauge sections (>6 mm) or code-governed fabrication, a brief stress-relief anneal at 750–850°C helps restore full HAZ toughness. Avoid hydrogen or nitrogen in shielding gas — both embrittle ferritic weld metal. FUSHUN METAL can supply matching ER444 filler wire for complete metallurgical compatibility.

FUSHUN METAL applies a seven-stage quality protocol for this premium Mo-bearing grade: (1) incoming chemistry by OES with LECO C/S; (2) Mo content verification — Mo 1.75–2.50% individually confirmed as the critical PREN driver; (3) Ti stabilization ratio audit — Ti ≥ 6 × (C+N); (4) in-process dimensional checks during rolling/forming; (5) post-annealing mechanical testing (tensile ISO 6892-1, hardness EN ISO 6506 on each bar/sheet end); (6) intergranular corrosion test per EN ISO 3651-2 (optional, recommended for welded-fabrication orders); (7) final dimensional/visual inspection. Full chain under ISO 9001 & AS9120B, EN 10204 3.1 documentation, traceable to melt. For critical applications, we offer pitting corrosion testing per ASTM G48 Method A.

Yes — and the economics become increasingly favorable as nickel prices rise. 444 contains no intentional nickel (Ni ≤ 0.50%), while 304 contains 8–10.5% Ni and 316L contains 10–13% Ni. The Mo content (2%) adds modest alloy cost but nowhere near the cost of 10% nickel at current LME prices. Typical pricing: 444 is ~15–20% cheaper than 304 and ~30–35% cheaper than 316L in sheet/coil form. When you factor in the elimination of SCC-related failures (a common warranty cost driver for 304/316L equipment), the total-lifecycle cost advantage is even greater. FUSHUN METAL provides competitive quotations with short lead times — inquire with your required dimensions for a current price.