Techniques to make the Duplex Stainless Steel Fasteners the right way…….

Great Steel & Metals

Want to fight the challenges of corrosion? Use Duplex and Super Duplex Grades of Stainless Steel offered by Great Steel & Metals that provides superior corrosion resistance. It works even at the time when 316 grade is not enough.

 Duplex Stainless Steel Fasteners (SAF 2205 or UNS S31803) or Super Duplex Stainless Steel Fasteners (SAF 2507 or UNS S32750) has important feature which includes its high level corrosion resistance which makes it superior to 304 or 316 grade Stainless Steel.

It is this feature of duplex stainless steel which when combined with high mechanical strength and ductility makes it a fit material for different kinds of applications.

Most often, the 316 Grade Stainless Steel is termed as ‘Marine grade’ – because it is ideal for marine environments. it makes one of the most robust allows which remains fit for high chloride environments. It is used for fastening on yack’s deck and other such uses.

And yes while it is often used and ideal for marine environments such as There are many places where fastener strength and integrity are important and here comes the role of stainless steel. if stainless fastener gets submerged in sat water, duplex would be the minimum requirement. A high degree of quality control is required in this matter and it needs to be ensured that the source is specialized in Duplex fastener manufacture.

Duplex Manufacturing Technologies

In the extremely careful temperature controlled environment, Duplex

Fasteners are manufactured with forged heads and rolled threads. They can also be CNC machined from either the round or hex bar -however, in the extreme circumstances too, they would be made with the help of forged heads and rolled threads. Also, it is a basic requirement for threads to be rolled rather than machined for ensuring the production of  smoother and stronger threads as compared to the machined/CNC threads.

With this process, the tread which comes out have strong yield, high surface finish, extreme hardness, as well as wear resistance. Temperature control also remains important during the process of Hot Forging the fastener head. Prolonged exposure to critical temperature should be avoided while heating Duplex otherwise it might produce unwanted Nitrides and Carbides. It is important to use the digital control equipment to heat through this temperature zone. It is then automatically removed from the heat source when the temperature becomes maximum for forging.

The Duplex item is then laser marked to ensure fastener’s traceability through the supply chain. One also needs to obtain Test Certificates.

Duplex Applications – where would you use Super Duplex over Duplex?

There are many applications which find usage of Duplex steels. They include piping systems and pumps as the process of good erosion and abrasion resistance is employed in their  techniques. Also, there are ), valves, heat exchangers, Keel Bolts which find a wide usage with certain items submerged in salt-water as well as other equipment.

Duplex comes with strong general corrosion resistance and is superior to grade 316 in lot many scenarios such as in giving resistance to inter-granular, pitting and crevice corrosion.

Super Duplex has much more greater pitting resistance. Overall, the inference is that 316 is good while Duplex is great and Super Duplex comes to be the best.

The approx PRE pitting corrosion values for 304 and 316 Stainless Steel along with Duplex as well as Super Duplex grades are as following:

304 = 17-20316 = 25-30Duplex = 30-38Super Duplex = >40

Great Steel & Metals, the leading duplex flanges manufacturer in India (

دوبلكس فلنجات offers premium quality of ( تصنيعstainless steel fasteners to meet the requirements of the customers.