Super duplex stainless steel 1.4462 has become a popular choice in the duplex stainless steel market with its excellent cost-effectiveness and reliable performance. SS1.4410 serves as a representative of super duplex steel that addresses the most severe corrosion challenges and is the ultimate solution when 2205 is insufficient.
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Features of Duplex Stainless Steel
High Strength: The duplex structure provides extremely high mechanical strength. The yield strength was typically twice that of standard austenitic stainless steels such as 316L. This means that wall thickness can be reduced under the same pressure requirements, resulting in lightweight designs and material cost savings.
Resistance to stress corrosion cracking (SCC): This is the primary reason for the development of duplex stainless steels. They offer exceptional resistance to SCC in chloride environments, far exceeding that of 304/316 stainless steels.
Resistance to pitting and crevice corrosion: Duplex steels significantly enhance their resistance to localized corrosion through the addition of molybdenum (Mo) and nitrogen (N), a property often quantified using the pitting corrosion resistance equivalent (PREN) value. PREN = %Cr + 3.3 × %Mo + 16 × %N.
Weldability: Modern welding techniques (such as TIG and MIG) can weld duplex steels well, but require strict control of heat input and interpass temperature to maintain the ideal phase balance.
Cost of 1.4462 and 1.4410
1.4462 contains more nickel, molybdenum, and chromium, and its raw material price is typically 30%-50% higher than 1.4410. This is a key economic factor to consider when selecting a suitable material.
Chemical properties astm 1.4462 VS astm 1.4410
| Grade | C≤ | Mn≤ | P≤ | S≤ | Si≤ | Ni | Cr | Mo | N | Cu |
| S32205 | 0.03 | 2 | 0.03 | 0.02 | 1 | 4.5–6.5 | 22.0–23.0 | 3.0–3.5 | 0.14–0.20 | - |
| S32750 | 0.03 | 1.2 | 0.035 | 0.02 | 0.8 | 6.0-8.0 | 24.0-26.0 | 3.0-5.0 | 0.24-0.32 | 0.5 |
Mechanical properties 1.4462 VS 1.4410
| Mechanical properties | Tensile, min, ksi[MPa] | Yield, min, ksi[MPa] | Elongation, %(min) | Hardness, HB(max) |
| S32205 | 95 [655] | 65 [450] | 25 | 293 |
| S32750 | 116 [800] | 80 [550] | 15 | 310 |
Machinability of s32205 and s32750
Cold Forming: 1.4462 has greater ductility, making it easier to perform cold bending, stamping, and other operations. Machining S32750 requires greater force and more careful processing to prevent cracking.
Hot Working: Both require a tightly controlled temperature range.
Welding: Both are weldable, but S32750 requires more demanding welding techniques. More precise control of heat input and interpass temperature, along with the use of more compatible, advanced welding consumables (such as 2594 grade), is required to ensure adequate nitrogen content and an ideal phase balance in the weld zone, preventing the precipitation of harmful intermetallic phases (such as sigma phase).
uns s31803 and uns s32750 Resistance to Pitting and Crevice Corrosion
S31803 (2205)'s PREN value (~35) makes it suitable for most moderate chloride environments, such as mild seawater and weakly acidic chloride solutions in chemical processes.
S32750 (2507)'s PREN value (>40) gives it pitting resistance approaching, and in some cases exceeding, that of Alloy 625 (Hastelloy). It can handle even more demanding environments, such as:
- Hot, concentrated seawater
- Chemical process fluids containing high chloride concentrations
- Acidic oil and gas environments (high H₂S and CO₂)
duplex 2205 and duplex 2507 Resistance to Stress Corrosion Cracking (SCC)
Both are superior to austenitic stainless steels. However, under extreme conditions of higher temperatures, higher chloride concentrations, and higher stresses, S32750's tolerance limit is much higher than 1.4462.
ss2205 and ss2507 General Corrosion
In many non-oxidizing acids, such as sulfuric acid and acetic acid, 1.4462 offers superior corrosion resistance due to its higher molybdenum content. In oxidizing acids, such as nitric acid, both perform well, with 1.4410 slightly superior due to its higher chromium content.
Select S31803 (2205) in the following situations
- Budget is limited, and its performance is sufficient to meet the application requirements.
- The operating environment is moderately corrosive (e.g., ambient seawater, low chloride concentrations).
- The application requires good cold forming processability.
- The wall thickness and weight of the equipment are not the most critical constraints.
S32750 (2507) must be selected in the following situations
- Extremely harsh environments: high chloride concentrations, high temperatures, high pressures, and high acidity (e.g., oil and gas wells with high H₂S).
- Reducing equipment weight is a primary goal. Leveraging its high strength allows for significant reductions in wall thickness, potentially offsetting some of the material costs.
- 1.4410 has experienced corrosion failure in similar applications, necessitating a higher level of safety.
- The media conditions require a PREN value above 40.
