Duplex steel 1.4462 for bolts

Duplex steel is a stainless steel with a microstructure of roughly equal parts ferrite and austenite. The combination unites the strength of ferrite with the corrosion resistance of austenite: the yield strength of 1.4462 is around twice that of 1.4571, and duplex is considerably more resistant to stress corrosion cracking and pitting in chloride-containing media. Super duplex grades such as 1.4410 improve both properties further for seawater and aggressive process media.

Where duplex bolts are used

Seawater systems and shipbuilding, offshore platforms, chemical and petrochemical plants, desalination, pumps and valves for chloride-containing media. The high strength allows smaller cross-sections than with austenitic steels, and the corrosion resistance makes coating unnecessary.

What matters in production

Duplex is difficult to machine: the cutting speed is limited, because above it the cutting edge burns, and the material work-hardens heavily during forming. RS Randack turns duplex with matched cutting data and rolls the threads. Parts are crack-tested using the dye penetrant method (PT); many specifications also require impact energy and ferrite content on the certificate.

What you should specify

Material number or ASTM grade, medium and temperature, required minimum values and tests, certificate type. Duplex is not always in stock, so let us know your delivery date early.