Super austenitic stainless steel (904L / 254SMO) has high corrosion resistance, strong acid resistance, pitting corrosion resistance, and stress corrosion resistance, and is used in high-end chemical, nuclear power, seawater, desulfurization, and precision equipment.

Ⅰ.What is Duplex Stainless Steel? Duplex Stainless Steel (DSS) is a stainless steel with a composition that is equal in both austenitic (e.g., 304/316) and ferritic stainless steel.

Metallographic structure: Austenitic + Ferritic ≈ 1:1

Inherently combines: High strength + Strong corrosion resistance + Good toughness

**Most typical examples:** 2205, 2507 Duplex steel = High-end stainless steel with double the strength, stronger corrosion resistance, greater durability, and lower cost.

Ⅱ.Core Differences Between Duplex Stainless Steel and Ordinary Stainless Steel (304 / 316L)

1. Different Strength (Most Crucial)

304/316L: Yield Strength ≈ 200MPa

Duplex Stainless Steel (2205): Yield Strength ≥ 450MPa → More than twice the strength of ordinary stainless steel → Can be made thinner, lighter, and lower cost

2. Different Corrosion Resistance

304: Sensitive to seawater and chloride ions

316L: Resistant to general corrosion, but moderately resistant to pitting/crevice corrosion

Duplex Stainless Steel: Particularly resistant to seawater, chloride ions, and stress corrosion → Suitable for coastal, chemical, desalination, shipbuilding, and oil and gas projects

3. Price and Cost-Effectiveness

More expensive than 304

Slightly more expensive than or close to 316L

However, considering overall lifespan, thickness, and maintenance costs → Cost-effectiveness is far superior to 316L

4. Application Scenarios

304: Decorative, kitchenware, general equipment

316L: Chemical, coastal, moderate corrosion

Duplex Stainless Steel: Seawater, oil and gas, high corrosion, high pressure, heavy structures

1. Classification

Based on alloy content and performance, the industry generally classifies duplex steel into 4 categories:

1. Lean Duplex

Representatives: 2101, 2304

Features: Inexpensive, a substitute for 316L

Corrosion resistance ≈ 316L, higher strength

2. Standard Duplex

Representative: 2205 (Most mainstream, highest sales volume)

90% of duplex steel exported is this

Strong corrosion resistance, high strength, and the most versatile

3. Super Duplex

Representative: 2507

High Cr, high Mo, high N

Extremely resistant to corrosion: seawater, oil and gas, strong acids, high-pressure conditions

4. Hyper Duplex

Representatives: 32707, etc.

Extreme conditions: deep sea, high temperature, high chlorine, strong corrosion

Low usage, high price

1. Core Product Materials
2. 2205 Duplex Stainless Steel (General Purpose Benchmark)

- International Grade: UNS S32205 / S31803, corresponding to Chinese National Standard 022Cr22Ni5Mo3N

- Microstructure: Austenitic + Ferritic duplex structure (ratio approximately 1:1), possessing excellent properties of both phases

- Standards: ASTM A240/A276/SA-182, covering the full range of plates/pipes/bars

2. 2507 Super Duplex Stainless Steel (For Extreme Working Conditions)

- International Grade: UNS S32750, corresponding to Chinese National Standard 022Cr25Ni7Mo4N, also known as SAF 2507

- Microstructure: High-alloy duplex structure, significantly improved chromium, molybdenum, and nitrogen content, achieving top corrosion resistance among duplex steels

- Standards: ASTM A790/A479, mainstream certification in high-end marine engineering and chemical industries

Key performance parameters

1. Precise Chemical Composition (Mass Fraction, %)
2. 2205 duplex stainless steel

2. 2507 Super Duplex Stainless Steel

1. Product Details

Mainstream product forms

Duplex stainless steel coils are renowned for their exceptional corrosion resistance and high mechanical strength, and are widely used in offshore engineering, seawater desalination, oil and gas pipelines, and harsh industrial environments. Unlike ordinary steel, they possess excellent resistance to chloride stress corrosion, pitting corrosion, and crevice corrosion. However, their performance may be limited in extremely high-temperature or highly oxidizing acidic conditions. Duplex stainless steel is available in various grades and surface treatments to suit different harsh operating conditions.

Duplex stainless steel coils use 2205, 2507, and 2304 duplex stainless steel sheets as raw materials to ensure superior quality of the finished product. The steel sheets undergo surface treatment through chemical and mechanical methods such as pickling, passivation, and polishing to improve corrosion resistance and surface finish. Subsequently, the treated steel sheets are cold-rolled using a cold rolling mill to ensure that their thickness and dimensional accuracy meet requirements. Finally, the cold-rolled stainless steel strips are slit into strips and coiled to produce duplex stainless steel coils. The finished coils are properly packaged for easy storage and transportation.

In order to ensure product quality, we will arrange professional personnel to check product quality, packaging, weight, hardness, etc., according to customer requirements of product specifications, looking for high-quality and cheap cooperative factories in China, to provide customers with one-stop procurement services and quality assurance.

Excellent packaging: waterproof paper and plastic film + iron cover + at least three strapping straps + strapping straps fixed on iron or wood pallets can effectively protect products from corrosion and various climate changes during transportation. Generally speaking, we ship from Shanghai, Tianjin, Qingdao and Ningbo ports. We have worked with many experienced shipping companies for a long time to find the most suitable mode of transportation for you.