Chemical composition analysis of S32750 duplex stainless steel: performance advantages and applications

S32750 (UNS S32750, EN 1.4410) is a super duplex stainless steel. Due to its excellent corrosion resistance, high strength, and good welding performance, it is widely used in petrochemical, marine engineering, seawater desalination, and other fields. The precise ratio of its chemical composition directly affects the mechanical properties and corrosion resistance of the material. This article will analyze the chemical composition of S32750 in detail and explore its impact on performance.

 

 

1. Chemical composition of S32750 duplex stainless steel

The chemical composition of S32750 complies with international standards such as ASTM A790, ASTM A928, EN 1.4410, and its typical composition is as follows:

Element	Content range (wt%)	Function analysis
Carbon (C)	≤0.03%	Reduce carbide precipitation and improve intergranular corrosion resistance
Chromium (Cr)	24.0-26.0%	Enhance oxidation resistance and pitting resistance
Nickel (Ni)	6.0-8.0%	Stabilize the austenite phase and improve toughness
Molybdenum (Mo)	3.0-4.0%	Improve chloride stress corrosion resistance
Nitrogen (N)	0.24-0.32%	Promote dual-phase balance and improve strength
Manganese (Mn)	≤1.2%	Improve hot working performance
Silicon (Si)	≤0.8%	Improve oxidation resistance
Phosphorus (P)	≤0.035%	Control impurities and reduce brittleness
Sulfur (S)	≤0.02%	Reduce hot brittleness

The role of key components
High chromium (Cr) + molybdenum (Mo) + nitrogen (N): makes S32750 have extremely high pitting resistance equivalent (PREN ≥ 40), suitable for high chloride ion environment (such as seawater, chemical media).

Low carbon (C): Reduces carbide precipitation in the heat-affected zone of welding and avoids intergranular corrosion.

Nitrogen (N): Promotes the balance of austenite-ferrite dual-phase structure, improves strength and corrosion resistance.

 

2. Effect of chemical composition on performance

(1) Corrosion resistance
Chloride corrosion resistance: High Cr, Mo, and N content make it perform well in seawater and salt spray environments.

Stress corrosion cracking (SCC) resistance: Better than 304/316 austenitic stainless steel, suitable for high-pressure and high-temperature environments.

(2) Mechanical properties
High strength: tensile strength ≥800 MPa, yield strength ≥550 MPa (about twice that of 316 stainless steel).

Good impact toughness: The dual-phase structure still maintains high toughness at low temperatures.

(3) Welding performance
Matching welding materials (such as ER2594) must be used, and heat input must be controlled to avoid embrittlement caused by precipitation of σ phase.

 

3. Application fields of S32750

Oil & Gas: Subsea pipelines, valves, pump bodies (resistant to H₂S/CO₂ corrosion).

Chemical equipment: reactors, heat exchangers, pickling equipment.

Desalination: high-pressure RO membrane shells, pump shafts.

 

4. Conclusion

S32750 duplex stainless steel, with its optimized chemical composition of S32750 (high Cr, Mo, N, low carbon), excels in corrosion resistance, strength, and weldability, making it an ideal choice for harsh industrial environments. Proper control of the composition and heat treatment process can maximize its performance advantages.