Super Duplex Stud Bolts​

In-house production

​Through our in-house production Esbjerg Oiltool A/S is able to produce up to approximately 1000 super duplex stud bolts per day (depending on size and length). We have base material from 1/2" to 1.1/2" in stock in form of threaded rods in grade FLT and nuts and we are able to produce super duplex stud bolts in any length (up to ~3000 mm) requested by our customers. The stud bolts can be delivered as stud bolts only or fitted with 1-2 or more super duplex heavy hex nuts according to customer specifications. Stud bolts larger than 1.1/2" can be sourced. Please contact us for more information. 

Stud Bolt Grades

Grade FLT

The base material for super duplex stud bolts to grade FLT (Fasteners Low Temperature) has been solution annealed at 1120 °C followed by quenching in water. This is then followed by strain hardening to raise the mechanical values. The material is Charpy V Notch tested at -101°C

Mechanical properties for Grade FLT Stud Bolts:

  • Tensile strength min. 860 MPa
  • Yield Strength (0,2% offset) min. 720 MPa
  • Elongation in 2" (50mm) or 4D min. 16%
  • Reduction of area min. 50%
  • Brinell Hardness max. 335Grade FG

Grade FG

​The base material for super duplex stud bolts to grade FG (Fastener Grade) is produced and tested in the exact same way as for grade FLT with the only difference that the Charpy V Notch testing is performed at -46 °C. The mechanical properties of grade FG is also identical to those of grade FLT.

Grade SA

​The base material for grade SA has also been solution annealed at 1120°C followed by quenching in water but with no subsequent strain hardening. This results in a lower strength compared to both grade FLT and grade FG. Charpy V Notch testing is performed at -46°C

Mechanical properties for Grade SA Stud Bolts:

  • Tensile strength min. 800 MPa
  • Yield Strength (0,2% offset) min. 550 MPa
  • Elongation in 2" (50mm) or 4D min. 25%
  • Reduction of area min. 50%
  • Brinell Hardness max. 290

Super Duplex

Typical applications​

Due to the excellent resistance to corrosion super duplex UNS S32760 stud bolts are especially suited for service in areas with corrosive environments:

  • Offshore Oil and Gas
  • Salt water applications
  • Paper production
  • Subsea
  • Chemical tanks and tankers
  • Desalination
  • Geothermal
  • Mining

​Super duplex names

The base material we use for stud bolts is UNS S32760 super duplex. Other names for this material are:

  • Zeron 100 - (Wikipedia has more about the history of Zeron 100 here)
  • 25Cr Duplex
  • Alloy 100 Super Duplex
  • EN 1.4501
  • Alloy 1.4501
  • A182 F55 (when used as forgings)
  • X2CrNiMoCuWN25-7-4
  • FLT Stud Bolts

Super duplex S32760 chemical composition

%

C

Si

Mn

S

P

Cr

Min

24,00

Max​

0.03

1,00

1,00

0,01

0,03

26,00

%

Ni

Mo

N

Cu

W

Min

6,00

3,00

0,20

0,50

0,50

Max

8,00

4,00

0,30

1,00

1,00

PREN for UNS S32760

​Pitting Resistance Equivalent Number (PREN) is a way to calculate the resistance to pitting corrosion for stainless steels enabling a theoretical comparison of different stainless steels and their resistance to pitting corrosion based on their chemical composition. There are various formulas being used for this calculation. The formular most often used is: PREN = Cr + 3.3Mo + 16N

For materials where tungsten has been added to the composition a different formular is used to reflect the positive effect tungsten has on the resistance to pitting corrosion. UNS S32760 super duplex is one of the materials with added tungsten. See the chemical composition above. In this case this formular is used: PREN = Cr + 3.3(Mo + 0.5W) + 16N

​The super duplex base materials used for stud bolts at Esbjerg Oiltool A/S will have a PREN > 40 - For comparison 316L stainless steel has a typical PREN of 23-28

​Contact

​Esbjerg Oiltool A/S

Håndværkervej 67
6710 Esbjerg V 

Denmark

Tel.: (+45) 75 15 64 00
E-mail: jakob@esbjergoiltool.dk 


CVR: 10458374