Benefits of Stainless Steel Material
Steels made of stainless are popular due to their excellent resistance to corrosion. They are made by altering the composition of different alloying elements. They are broadly classified intoferritic, austenitic martensitic and duplex precipitation stainless steels that are hardened. This article will discuss the brief background, classification, properties and the applications for Duplex Stainless steel.
Duplex stainless steels feature a microstructure that is composed of austenitic and ferritic steels. The mechanical features associated with Duplex stainless steel depend on the proportions of austenite and ferrite elements inside the composition.
Duplex stainless steel was first thought of in the 1930s. During this time, keeping chemistry in check was difficult because of manufacturing limitations. However, it was utilized in certain applications. As technology advanced and especially with the introduction of decarburization in the 1960s manufacturing of stainless duplex steel was practical.
Duplex 2205 which is often referred to as the “workhorse” for duplex grades was invented during this time. The 1980s witnessed the advent of super-high quality Super and Duplex Hyper grades. These new grades are able to withstand even the most corrosive conditions. Duplex stainless steel has been introduced into in the industry of oil and gas through the development of these premium Super Duplex and Hyper.
The classification of Duplex Stainless steel
Below are a few most popular Duplex grades of stainless steel.
|Name of the common||UNS Number||BEN number||Wnr|
|Duplex||2205 (F51, F60)||S31803, S32205||1.4462|
|Super Duplex||2507 (F53)||S32750||1.441|
|Hyper Duplex||Sandvik SAF2707||S32707|
Duplex Stainless Steel grades exhibit corrosion resistance similar to or superior to the austenitic grades. The higher Chromium content in combination with Molybdenum gives it greater resistance to crevice corrosion and pitting. The Pitting Resistance Equivalent number (PREN) will be utilized to determine the grade by the resistance they have to pitting. The higher the PREN number, greater will be the resistance to corrosion from pitting.
Also read use of Duplex Flanges
Stress Corrosion Cracking (SCC) Resistance
Austenitic grade are vulnerable to SCC but ferritic grades are more resistant to it. Duplex stainless steels have superior SCC resistance than austenitic grades however they are weaker than ferritic stainless steels. Duplex stainless steel grades SCC starts in the austenitic area but is stopped in ferritic crystal structures near the boundary, thereby stopping the propagation of cracks and extending the time.
Duplex Stainless steels are stronger in mechanical resistance than austenitic grades and ferritic grades. They allow for the use of thinner sections and aids to reduce weight.
Welding can be difficult when compared to austenite. A precise control of temperature input and cooling rates is necessary to prevent the formation of undesirable intermetallic phase.
Benefits in Duplex stainless steel over austenitic counterparts-
Stronger strength allows the using thinner gauges, which are useful for lighter fabrications
The prices of stainless steelare heavily influenced by one specific commodity i.e. Nickel. Duplex stainless steels have a lower Nickel content, which makes it resistant to price fluctuation.
The two factors above are what make Duplex stainless steel quite affordable with better properties for certain applications.
Applications and Uses of Duplex Stainless Steels
Chemical processing, storage and transport tanks, pressure vessels pipes, heat exchangers
Exploration of oil and gas as well as processing equipment, such as tubing, pipes and heat exchangers
Marine and other high-chloride environments
Pulp and paper industry – bleaching equipment, digesters and stock-handling equipment
Cargo tanks for trucks and ships
Equipment for food processing
Check additional information about Super Duplex Pipe
|1.4462 (F51 & F60)||The Round Bar, Billets & Ingots|
|1.4410 (F53)||Bars with round edges, Billets & Ingots|
|1.4821||Bars with round edges, Billets & Ingots|
|1.4460 (329)||Bars with round edges, Billets & Ingots|
|1.4362 (2304)||Bars with round edges, Billets & Ingots|