What is 1.4521 Stainless Steel?
Mar 17, 2026
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1.4521 stainless steel, commonly known as 444 or UNS S44400, is a molybdenum-alloyed ferritic stainless steel with excellent corrosion resistance, particularly against chloride-induced pitting and crevice corrosion. Its addition of molybdenum and titanium stabilization provides performance approaching that of 316L austenitic stainless steel in many environments, while maintaining the lower cost and favorable physical properties of ferritic grades. It is widely used in water heaters, heat exchangers, and food processing equipment.
This high-performance ferritic grade is standardized under key international systems.
| Standard | Equivalent Grade |
|---|---|
| EN (Europe) | 1.4521 |
| ASTM/AISI (USA) | 444, UNS S44400 |
| JIS (Japan) | SUS444 |
| KS (Korea) | STS444 |
Its composition includes molybdenum for enhanced corrosion resistance and titanium/niobium for stabilization.
| Element | C | Si | Mn | P | S | Cr | Mo | Ti+Nb |
|---|---|---|---|---|---|---|---|---|
| Content (%) | ≤ 0.025 | ≤ 1.0 | ≤ 1.0 | ≤ 0.04 | ≤ 0.03 | 17.5 - 19.5 | 1.75 - 2.5 | ≥ 0.20+4(C+N) |
It offers good mechanical properties combined with excellent corrosion resistance.
| Property | Yield Strength (Rp0.2) | Tensile Strength (Rm) | Elongation (A) | Hardness (HB) |
|---|---|---|---|---|
| Typical Value | ≥ 280 MPa | 420 - 640 MPa | ≥ 20% | ≤ 200 |
Key Characteristics and Applications of 1.4521 / 444
Excellent Chloride Resistance: The molybdenum addition provides significantly better resistance to pitting and crevice corrosion in chloride-containing environments than standard ferritic grades, approaching that of 316L.
Stress Corrosion Cracking Resistance: Being ferritic, it offers inherent resistance to chloride stress corrosion cracking, which can affect austenitic grades like 304 and 316.
Stabilized Structure: Titanium and niobium stabilization prevents sensitization during welding, maintaining corrosion resistance in welded areas.
Low Thermal Expansion: Lower coefficient of thermal expansion than austenitic grades, beneficial for applications with thermal cycling.
Primary Applications:
Water Heaters: Storage tanks, heat exchanger tubes, and flue pipes in residential and commercial water heaters.
Heat Exchangers: Tubing for heat recovery systems, solar water heaters, and industrial heat exchangers.
Food Processing: Equipment for handling food products with moderate chloride content.
Brewing and Beverage: Tanks and piping for beer, wine, and soft drink processing.
Architectural: Roofing, cladding, and gutters in coastal or industrial environments.
Automotive: Exhaust components requiring higher corrosion resistance than 409/439.
How does 444 (1.4521) compare to 316L (1.4404) stainless steel?
444 offers corrosion resistance comparable to 316L in many environments, particularly against chloride pitting and general corrosion, while providing superior resistance to chloride stress corrosion cracking. It has higher thermal conductivity, lower thermal expansion, and is magnetic, whereas 316L is non-magnetic. 444 is typically more cost-stable due to its lower nickel content (no nickel addition). However, 316L offers better formability, higher toughness at cryogenic temperatures, and better weldability for complex fabrications. 444 is often chosen as a cost-effective alternative to 316L for applications like water heaters and heat exchangers where its properties are well-suited.
What are the welding considerations for 444 stainless steel?
444 has good weldability due to its stabilization with titanium and niobium. Low heat input welding techniques are recommended to minimize grain growth in the heat-affected zone. Matching filler metals are available, though austenitic fillers like 309L or 316L are often used for dissimilar welds. Preheating is generally not required, but post-weld cleaning is important to restore corrosion resistance. The stabilized composition prevents sensitization, so post-weld heat treatment is not necessary for corrosion resistance. For optimum corrosion performance in severe environments, consideration should be given to filler metal selection to match or exceed the base metal's corrosion resistance.
Looking for a Reliable Supplier of 1.4521 / 444 Stainless Steel?
GNEE Steel supplies high-performance 444 (1.4521) stainless steel in sheet, coil, plate, tube, and strip forms, ideal for water heater, heat exchanger, and food processing applications. We provide full material certification (EN 10204 3.1) and processing support including cutting, bending, and welding services. If you have any requirements, please feel free to contact us.
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