Duplex vs 316 stainless steel: How to choose materials?

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When choosing stainless steel materials in industrial, marine, or structural engineering projects, duplex stainless steel and 316 stainless steel are the two most commonly compared materials. They all have excellent corrosion resistance, but there are significant differences in strength, cost, and performance in harsh environments.

This article will provide a detailed analysis of the differences between duplex stainless steel and 316 stainless steel to help you choose the appropriate material.

Duplex vs 316 stainless steel Definition and Characteristics

Definition and Characteristics of 316 stainless steel

316 stainless steel belongs to austenitic stainless steel and contains molybdenum (Mo) element, so its corrosion resistance in chlorine containing environments is better than that of 304 stainless steel.

Main Features

Excellent corrosion resistance performance
Good formability and weldability
Excellent resistance to pitting and crevice corrosion
Basically non-magnetic in annealed state
Wide market supply and easy processing

Definition and Characteristics of duplex stainless steel

Duplex Stainless Steel has a duplex structure consisting of approximately 50% austenite and 50% ferrite, which combines high strength and excellent corrosion resistance.

Main Features

The strength is about twice that of 316 stainless steel
Excellent resistance to stress corrosion cracking (SCC)
Excellent performance in high chloride ion environments
Low nickel content, relatively less price fluctuation
Good anti fatigue performance

S22053 duplex vs 316 stainless steel pipe

S22053 duplex stainless steel

316 stainless steel seamless pipe welded pipe

316 stainless steel pipe

Comparison between duplex vs 316 stainless steel

Chemical Composition

Element 316 stainless steel Duplex stainless steel
Chromium (Cr) 16-18% 21–23%
Nickel (Ni) 10–14% 4.5–6.5%
Molybdenum (Mo) 2–3% 2.5–3.5%
Nitrogen (N) – 0.1–0.3%

Performance comparison

Performance 316 Stainless Steel Duplex Stainless Steel
Metallographic structure Austenite Austenite+Ferrite
Yield strength ~200-300 MPa ~450-550 MPa
Tensile strength ~500-700 MPa ~700-900 MPa
Corrosion resistance Excellent Better (especially resistant to chloride ions)
Stress Corrosion Cracking Resistance Moderate Extremely Strong
Welding performance Very good Good (requires control of heat input)
Cost Low initial cost High unit price but can reduce material thickness
Is there magnetism None (annealed state) Slightly magnetic

Differences between processing and welding

Processing factors 316 stainless steel Duplex stainless steel
Cold forming Easier Requires greater forming force
Welding High fault tolerance Need to control heat input
Machining Medium difficulty Slightly difficult

316 is more suitable for complex processing and large-scale welding scenarios, while duplex steel has stricter requirements for welding processes.

2205 duplex plate

duplex seamless tube

Purchase suggestions

Suitable for choosing 316 stainless steel:

1 · limited budget
2 · Corrosion environment is relatively mild
3 · Complex molding or welding is required
4 · Conventional equipment in the food or pharmaceutical industry

Suitable for selecting duplex stainless steel:

1 · Seawater or high chlorine environment
2 · Requires high-strength and lightweight design
3 · Worried about stress corrosion cracking
4 · Pursuing long-term durability

Summary

Both of these materials are excellent, but with different focuses:

  • 316 stainless steel: strong universality, corrosion resistance, easy processing.
  • Duplex phase stainless steel: higher strength, stronger resistance to chlorine corrosion, and longer service life in harsh environments.

If the project involves marine engineering, chemical or high salt environments, duplex stainless steel is usually a more reliable long-term choice; In the general industrial and construction fields, 316 is a classic material with extremely high cost-effectiveness.

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