[Dry information] Comparison of the advantages and disadvantages of duplex stainless steel and austenitic stainless steel

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What is duplex stainless steel?

The ideal metallographic structure of duplex stainless steel is 50% ferrite and 50% austenite. Generally, the minimum phase content must reach 30%. It has the advantages of both austenitic stainless steel and ferritic stainless steel. Commonly used grades are: 2304, 2205, 2507, 2707, etc. Generally speaking, austenitic stainless steel is non-magnetic or weakly magnetic, while duplex steel is magnetic. In other words: it has the characteristics of stainless steel and the characteristics of carbon steel!

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What are the advantages of duplex steels over austenitic stainless steels?

1. The yield strength is more than twice that of commonly used 304, 304L, 316, 316L and other austenitic stainless steels, and it has sufficient plasticity and toughness required for molding. The wall thickness of equipment components made of duplex stainless steel can be reduced by 30-50% compared with 316L, which is beneficial to reducing costs.

2. No matter under dynamic or static load conditions, it has higher energy absorption capacity than austenitic stainless steel. This structural part can cope with unexpected accidents such as collisions, explosions, etc. Duplex stainless steel has obvious advantages and has practical application value.

3. High strength, significantly improved resistance to intergranular corrosion and chloride stress corrosion, and excellent pitting corrosion resistance

4. Excellent resistance to stress corrosion cracking. Even economical duplex stainless steels (such as 2304) have higher resistance to stress corrosion cracking than austenitic stainless steels. Especially in environments containing chloride ions, stress corrosion is a prominent problem that ordinary austenitic stainless steels cannot solve. .

5. Has good local corrosion resistance. Compared with austenitic stainless steel with a similar alloy content, its wear corrosion resistance and fatigue corrosion resistance are better than austenitic stainless steel.

6. The corrosion resistance of 2205 duplex stainless steel, which is the most commonly used in many media, is better than that of ordinary 316L austenitic stainless steel, while super duplex stainless steel has extremely high corrosion resistance in some media, such as acetic acid and formic acid. It can even replace high-alloy austenitic stainless steel and even corrosion-resistant alloys.

7. The linear expansion coefficient is lower than that of austenitic stainless steel and close to that of carbon steel. It is suitable for connection with carbon steel, such as the production of composite plates or linings.

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What are the disadvantages of duplex steel compared to austenitic stainless steel?

1. The universality and versatility of applications are not as good as those of austenitic stainless steel. For example, its continuous use temperature must be controlled below 250 degrees Celsius to avoid phase transformation.

2. Its plastic toughness is lower than that of austenitic stainless steel, and its cold and hot processing technology and forming performance are not as good as austenitic stainless steel.

3. There is a medium-temperature brittle zone, and the process system of heat treatment and welding needs to be strictly controlled to avoid the appearance of harmful phases and damage to performance.