What Is 1.4521 Stainless Steel?
1.4521 stainless steel, also known as AISI 444 or X2CrMoTi18-2, is a ferritic stainless steel containing chromium, molybdenum, and stabilizers such as niobium or titanium. It offers excellent corrosion resistance (particularly resistance to pitting, crevice corrosion, and stress corrosion cracking), good mechanical properties, and formability. Common applications include exhaust systems, heat exchangers, hot water tanks, and various industrial components.
What Is 1.4401 Stainless Steel?
1.4401 stainless steel, commonly known as Grade 316, is an austenitic chromium-nickel-molybdenum alloy featuring high corrosion resistance, particularly against chlorides and non-oxidizing acids. As a versatile "marine grade" steel, it offers superior pitting resistance compared to 304, along with excellent strength, toughness at low temperatures, and good weldability.
1. General Comparison
| Feature |
1.4521 (AISI 444) |
1.4404 (AISI 316L) |
| Microstructure |
Ferritic |
Austenitic |
| Magnetism |
Magnetic |
Non-magnetic |
| Nickel Content |
Very Low (≤ 1.0%) |
High (10.0 - 13.0%) |
| Stabilization |
Stabilized with Ti and/or Nb |
Low Carbon (L-grade) |
| Main Advantage |
Resistant to SCC, Price stability |
Formability, Toughness at low temp |
2. Chemical Composition ( - % by weight)
| Element |
1.4521 (X2CrMoTi18-2) |
1.4404 (X2CrNiMo17-12-2) |
| Carbon (C) |
≤ 0.025 |
≤ 0.030 |
| Chromium (Cr) |
17.0 - 20.0 |
16.5 - 18.5 |
| Molybdenum (Mo) |
1.70 - 2.50 |
2.00 - 2.50 |
| Nickel (Ni) |
- |
10.0 - 13.0 |
| Nitrogen (N) |
≤ 0.035 |
≤ 0.10 |
| Titanium (Ti) |
0.15 + 4(C+N) to 0.80 |
- |
3. Mechanical Properties (Typical at Room Temp)
| Property |
1.4521 |
1.4404 |
Yield Strength (Rp0.2) |
≥ 320 MPa |
≥ 200 - 240 MPa |
Tensile Strength (Rm) |
420 - 640 MPa |
500 - 700 MPa |
Elongation (A50mm) |
≥ 20% |
≥ 40 - 45% |
| Hardness (HB) |
≤ 230 |
≤ 215 |
| Toughness (Impact) |
Moderate (drops at low temp) |
Excellent (even at cryogenic temp) |
4. Physical Properties
| Property |
1.4521 |
1.4404 |
| Density ( kg/dm ³) |
7.7 |
8.0 |
| Thermal Conductivity (W/m·K) |
23 |
15 |
Thermal Expansion (10−6/K) |
11.0 (Lower - better for cycling) |
16.0 (Higher) |
| Modulus of Elasticity (GPa) |
220 |
200 |
1.4401 vs 1.4521 Stainless Steel: Corrosion Resistance
1.4521 (AISI 444) and 1.4401 (AISI 316) offer similar, high-level corrosion resistance, with 1.4521 often superior in chloride-rich environments due to higher molybdenum. 1.4521 is a stabilized ferritic steel (no nickel) with excellent resistance to pitting, crevice corrosion, and SCC, whereas 1.4401 is an austenitic steel (nickel-bearing) prone to stress corrosion cracking over 60°C.
1.4401 vs 1.4521 Stainless Steel: Machinability
When comparing the machinability of 1.4401 (AISI 316) and 1.4521 (AISI 444) stainless steels, the key difference lies in their material family structure: 1.4401 is austenitic, while 1.4521 is ferritic.
1.4521 is generally easier to machine than 1.4401. Because 1.4521 is a ferritic steel, it typically offers better machining performance, higher cutting speeds, and lower tool wear compared to 1.4401, which is austenitic and prone to work hardening.
1.4401 vs 1.4521 Stainless Steel: Weldability
Both 1.4401 (AISI 316) and 1.4521 (AISI 444) are highly corrosion-resistant steels, but they belong to different families and have distinct weldability characteristics.
1.4401 (Austenitic): Considered easy to weld, but sensitive to intergranular corrosion in thick sections due to carbon content (unless using 1.4404 low-carbon version).
1.4521 (Ferritic): Stabilized with titanium/niobium, offering excellent corrosion resistance in welds, but weldability is better in thinner sections; requires caution with larger thicknesses.
When to Choose Which:
Choose 1.4404 (316L) for superior corrosion resistance in severe chemical applications, deep drawing, and where non-magnetic properties are required.
Choose 1.4521 (444) for applications requiring high corrosion resistance along with higher strength, lower thermal expansion, and resistance to chloride-induced cracking, often at a lower cost due to lower nickel content.
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