Stainless steel is one of the basic materials used in the metal industry, and by manufacturers of steel or metal products. This is mainly due to the fact that stainless steel has very high corrosion resistance, mechanical strength and durability. Among them, duplex steel deserves special attention, which effectively combines the features of austenitic and ferritic steel. It is particularly desirable in the industry due to its unique utility properties and mechanical parameters. Why are duplex stainless steels so important in the world of modern industry?
- Chemical composition of duplex steel
- Mechanical properties of duplex stainless steel and superduplex steel
- The specificity of duplex steel and superduplex structures
- What is made of duplex steel and its application
- Wrapping up
Chemical composition of duplex steel
The chemical composition of duplex steel includes chromium, nickel, and molybdenum. A small, 5% addition of nickel means that the chemical composition of duplex stainless steels can be enriched with nitrogen, which is an element responsible for maintaining a stable two-phase structure. Standard duplex stainless steels contain 0.15% nitrogen, and super duplex steels contain 0.3%.
When discussing the chemical composition of duplex steel, it is also worth mentioning the reduced carbon content. Usually, steels are found that do not have more than 0.03% carbon in their composition.
Trace amounts of manganese, tungsten, copper can also be observed in duplex stainless steel.
Mechanical properties of duplex stainless steel and superduplex steel
When discussing the chemical composition of duplex steel, it is also worth mentioning the reduced carbon content. Typically, steels are found that do not have more than 0.03% carbon in their composition.
Trace amounts of manganese, tungsten, copper, or molybdenum can also be observed in duplex stainless steel.
It is also an element that leads to the stabilisation of ferrite and the reduction of stress corrosion cracking.
It is also worth mentioning copper, which improves the corrosion resistance (intergranular, pitting, atmospheric corrosion) of duplex steel. This is very important in the case of using this special stainless steel in the production of elements exposed to external conditions.
Molybdenum is an element that increases the resistance of duplex stainless steels to acetic acid and sulphuric acid.
The specificity of duplex steel and superduplex structures
Two phase microstructure is a combination of austenitic stainless steels and ferritic stainless steels. The proportions in creating this mixture are 50/50.
Creating such a stable mixture makes it much more durable than standard stainless steel, austenitic stainless steel, or ferritic steel. Duplex steel is a stainless steel characterised by a higher level of plasticity and reduced production costs, which may be important for potential investors in duplex stainless steel structures or products.
Super duplex and duplex stainless steel is distinguished by resistance to stress corrosion, cracking and good weldability. The aforementioned 50/50 ratio is a conventional ratio, because you can also buy duplex steel or super duplex stainless steel with a greater or lesser content of ferrite and austenite. In this way, various duplex stainless steel alloys are created, which can be more durable, harder, more resistant to stretching and impact.
What is made of duplex steel and its application
The wide range of applications of duplex steel and super duplex stainless steel means that there is great interest in these alloys in many industries.
Both types of steel are specialised materials that have a unique microstructure, and therefore exceptional mechanical properties and corrosion resistance.
Duplex steels are used in the maritime industry—in particular in structures and infrastructure that come into contact with seawater and in installations used for oil and gas extraction. This is also a steel that, due to its properties, can be used in the shipbuilding industry.
This steel can also be used to make elements that enable the safe transport of hazardous materials, which include various toxic substances and chemicals.
The combination of austenitic and ferritic stainless steels allows the production of an alloy that is used in the production of seamless pipes, tanks, pipelines, installation elements exposed to corrosive factors. It is also a material that allows the production of installations in contact with salt, e.g. for water desalination, or with sewage treatment plant infrastructure.
Wrapping up
In summary, duplex and super duplex stainless steel are in many cases irreplaceable alloys used successfully in many industries. The selection of the right type of this steel depends primarily on the working environment in which it is to be used, as well as on the efficiency and strength resulting from the conditions of the specific workplace. However, the use of this steel translates into a higher level of durability, can affect the safety of use and become an economical solution in many demanding engineering projects.