Difference Between Duplex and Super Duplex Fasteners

Duplex and Super Duplex Fasteners Overview

Although both duplex and super duplex are chromium, molybdenum, and nickel alloys. They also feature a mixed austenite-ferrite structure, which offers them better mechanical and physical qualities than separate austenitic and ferritic stainless steel classes.

The quantity of chromium and molybdenum in duplex and super duplex steel fasteners is the fundamental difference. Chromium concentration in super duplex grade stainless steel ranges from 24 to 26 percent, while chromium content in duplex grade stainless steel can range from 19 to 32 percent.  Duplex steel fasteners have a molybdenum content of 3% and a nickel content of 5%–6%, whereas super duplex steel fasteners have a molybdenum content of 4% and a nickel content of 7%. 

Another difference is that the inclusion of nitrogen is another distinction between duplex and super duplex steel. Nitrogen improves both the yield strength and the pitting resistance of super duplex stainless steel. In the presence of nickel, nitrogen additionally stabilizes the austenite effect.

The higher amount of chromium and molybdenum in super duplex stainless steel results in increased corrosion resistance and tensile strength that is substantially higher than the duplex stainless steel fastener. 

Since Duplex Steel Product Fasteners grades are more alloyed than duplex stainless steel fasteners, they provide a number of benefits, including exceptional resistance to chloride stress cracking and high toughness.  

Welding duplex and super duplex stainless steel fasteners is simple since they both have strong weldability and may be welded with the use of filler metals. For welding, neither of these stainless steel grades need pre- or post-heat treatment.  When compared to austenitic grade stainless steel, both duplex and super duplex fasteners have a higher tensile strength, so the cost of designing and manufacturing a product can be reduced. The product’s walls can be thinned, which reduces both the weight and the cost of the product.

The mechanical and physical properties of both duplex and super duplex steels are comparable to a high degree. For example, if duplex steel has a high mechanical strength, super duplex steels have a very high mechanical strength.

Although the distinctions between duplex and super duplex stainless steels can be seen in terms of chromium, nickel, molybdenum, and tungsten content, the addition of these elements makes super duplex stainless steels more complex to produce. The addition of these elements to a super duplex stainless steel alloy promotes the production of intermetallic phases. The formation of intermetallic phases can help to decrease the influence of strength of this grade drastically. 

While the element content varies between duplex and super duplex alloys, the higher tensile strength and corrosion resistance are the most noticeable differences. However, the mechanical and physical qualities of these grades are very comparable. As a result, in comparison to both Ferritic and Austenitic stainless steel grades, both of these grades can be considered the best because of their increased weldability, ductility, corrosion resistance, and high tensile strength.  

Products of Duplex 

The products vary in a wide variety of duplex fasteners and Super Duplex Fasteners. 

Duplex Fasteners products are stainless steel materials and they have equal portions of ferrite and austenite. This grade is the most popular variety and this two-phase material is a significant upgrade from 316 stainless steel in terms of both yield strength and corrosion resistance. 

Duplex Steel screws 

• 12 Point Screws
• Button Head Cap Screws
• Flat Head Screws
• Hex Head Cap Screws
• Pan Head Screw
• Security Screws
• Self Drilling Screws
•  Set Screws
• Socket Head Cap Screws

Duplex Steel Bolts

• Hex Head Bolts
• Shoulder Bolts
• Wedge Anchor Bolts

Duplex Nuts

• Hex Nuts
• Lock Nuts

Duplex Studs & Threaded Rod

• Studs
• Threaded Rod
• Weld Studs

Products of Super Duplex 

Super Duplex products are superior to duplex products in terms of corrosion, resistance and mechanical stregthn. They are resistant to chloride corrosion with high resistance strength. 

• Pipes and Tubes
• Round bar
• Sheets, plates and coils 
• Flanges
• Socket Weld Fittings
• Buttweild Pipe fittings
• Fastners 
• Instrumentation fittings

Conclusion

Dinesh Tube stands behind our products, a team of our experienced engineers, we dedicate to complex & strict defined requirements, we have manufactured best quality fasteners based on complex drawings where many companies have refused to manufacture the same to our customers because of their complexity & requirements of special grades. We cater to the needs of our customers. For more updates visit our website.