Duplex stainless steels offer a combination of the properties of austenitic and ferritic varieties of steel. They provide the best of both worlds by combining the greatest qualities of both, thereby offering a robust variety of steel with very few weaknesses. Moreover, duplex stainless steel is a more cost-effective option than the other different alloys of steel.
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Nonetheless, how will you determine whether duplex stainless steel is the right choice of steel alloy for your project?
In this article, we shall delve into the details of this unique variety of steel, taking you through its properties, benefits, and applications so that you may make informed decisions about the applicability of duplex stainless steel in your projects.
Definition of duplex stainless steel
The double-phase microstructure has led to the nomenclature of duplex stainless steel. Most duplex stainless steel composition is usually characterised by 50% ferrite and 50% austenite, with some differences that come with the grading.
Properties of duplex stainless steel
This double-phase microstructure leads to the properties of duplex stainless steel being a combination of the best traits of both varieties of steel used in creating the alloy. The minor differences between the two kinds of steel used only add to the durability, quality, and robustness of the duplex stainless steel, making it a better version of either of the two kinds of steel.
- Duplex stainless steel is usually more robust than ferritic varieties of stainless steel. And the strength of duplex stainless steel can often be almost double that of austenitic stainless steel.
- The magnetic properties of duplex stainless steel are different than the non-magnetic austenitic varieties of steel.
What is duplex stainless steel composed of?
Similar to other families of stainless steel, the precise metallurgic composition of duplex stainless steel differs according to grade. However, common components across grades are as follows:
- Carbon
- Manganese
- Chromium
- Silicon
- Nickel
- Sulphur
- Phosphorus
Copper, nitrogen, and molybdenum may also be used in the alloy to meet specific ends.
What are the grades of duplex stainless steel?
As with other varieties of steel, duplex stainless steel also comes in varying grades with different properties. Some of the available duplex stainless steel grades are
- 2304
- 4521
- 4501
- 4404
- 2507
- 4301
- 254 SMO,
- S32001
- S31803
- S32520
- S32205
- S32304, and
- LDX 210
Duplex 2304 stainless steel, also known as lean duplex grade, exhibits very high resistance to splitting due to stress corrosion, high machinability, excellent weldability, elevated thermal conductivity, and superior mechanical strength.
On the other hand, a super duplex stainless steel grade like 2507 stainless steel is equipped with a higher percentage of chromium, molybdenum, and nickel. Therefore, it exhibits enormous resistance to corrosion and pitting.
The qualities of duplex stainless steel
Although duplex stainless steel is less widely used than austenitic or ferritic varieties of steel, its unique properties entail several benefits. Some of them are as follows:
- Robust strength: Most duplex stainless steel grades are almost twice as strong as standard austenitic and ferritic grades of stainless steel.
- Excellent ductility and toughness: Duplex stainless steel is often tougher than austenitic or ferritic grades of stainless steel. It also has better properties of formability under pressure. While it may present lower values than certain austenitic steel grades, the unique microstructure of duplex stainless steel ensures both better ductility and improved toughness.
- Extremely high corrosion resistance: The corrosion resistance of duplex stainless steel is usually the same or sometimes higher than that offered by standard austenitic grades of stainless steel. Certain varieties of duplex stainless steel which are characterised by high molybdenum, chromium, and nitrogen content may exhibit excellent resistance to both chloride pitting and crevice corrosion.
- Easy weldability: Duplex stainless steel varieties offer excellent weldability. They are amenable to almost all common welding processes. Further, duplex stainless steel grades are characterised by low thermal expansion which leads to reduced distortion and residual stresses post-welding.
- Cost-effective: As mentioned before, duplex stainless steel is a more cost-effective option as compared to standard grades of austenitic or ferritic steel. This is because duplex stainless steel grades require lower percentages of nickel and molybdenum content. The enhanced strength and corrosion resistance of duplex stainless steel also ensure more long-term cost-effectiveness as compared to other varieties of stainless steel.
Read more: Comprehensive Information on Different Grades of Steel Bars and Their Applications
Some weaknesses of duplex stainless steel
Since duplex stainless steel is characterised by an amalgamation of the properties of austenitic and ferritic steel varieties, certain essential features of both these varieties may be compromised in duplex stainless steel.
For example –
- Duplex stainless steel, while exhibiting admirable anti-corrosion properties, is not as resistant to stress and corrosion-induced cracking as its ferritic counterparts.
- Duplex stainless steels of greater strength also offer greater resistance to machining.
Applications of duplex stainless steel
The qualities of robust strength, corrosion resistance, easy weldability, and cost-effectiveness make duplex stainless steel an irreplaceable raw material for diverse uses across a range of industries.
The applications of duplex stainless steel include:
- Construction
- Chemical processing units
- Paper and pulp production industries
- Parts and components in naval industries
- Water treatment, drilling, and desalinisation operations
- Pollution control machinery
- Hot water and brewing tanks
Duplex stainless steel – the other name for durability and toughness
The unprecedented strength and resistant quality of duplex stainless steel make it find application as a common raw material for use across various kinds of industries. Hopefully, this guide will help you understand about duplex stainless steel and purchase according to your specific needs.
Find the best quality duplex stainless steel in India at Sree Metaliks Limited
Sree Metaliks Limited is a renowned name in the Indian market for stainless steel. The company offers high-quality stainless steel of different varieties and grades across a wide variety of industries in India.
If you wish to know more about our products or require expert help with your stainless steel requirements, do not hesitate to contact us today!