What are Duplex Bolts?
Duplex bolts are made of duplex stainless steel material through cold heading machine header molding, through the rolling machine to form the thread of a special material bolts, because of the special chemical composition and mechanical properties of duplex stainless steel, has a high resistance to intergranular corrosion and resistance to chloride stress corrosion performance.
Duplex Bolts Factory
- Ding Fasteners
- N0.52 Qinfen Rd, Haiyan Zhejiang China
- [email protected]
- 0086-13819377033
- Walter Chou
Performance Characteristics of Duplex Bolts
- Molybdenum-containing duplex stainless steel fasteners have good chloride stress corrosion resistance at low stress.
General 18-8 austenitic stainless steel bolts in more than 60 ° C neutral chloride solution is prone to stress corrosion fracture, in trace chlorides and hydrogen sulfide industrial media are present in the tendency to produce stress corrosion fracture, and duplex stainless steel bolts in this type of stainless steel manufacturing heat exchangers, evaporators and other equipment but has good resistance.
- Duplex stainless steel screws and nuts containing molybdenum have good pore corrosion resistance. In the same pore corrosion resistance equivalent value (PRE = Cr% + 3.3Mo% + 16N%), duplex stainless steel bolts and austenitic stainless steel bolts with similar critical pore corrosion potential.
- S31803/2205 duplex bolts and austenitic stainless steel pore corrosion resistance is comparable to AISI 316L. Containing 25% Cr, especially nitrogen-containing high chromium duplex stainless steel bolts 2507 pore and crevice corrosion resistance exceeds that of AISI 316L.
Duplex bolts have good resistance to corrosion fatigue and wear corrosion performance. Under the conditions of certain corrosive media, it is suitable for making pumps, valves and other power equipment.
Duplex stainless steel screws have good comprehensive mechanical properties. Have high strength and fatigue strength, yield strength is 18-8 type austenitic stainless steel screws 2 times, yield strength up to 400Mpa ~ 550MPa. solid solution elongation of 25%.
Material Classification of Duplex Bolts
Low Alloy Type Duplex Bolts
Representative grade UNS S32304 (23Cr-4Ni-0.1N), the steel does not contain molybdenum, PREN value of 24-25, in terms of stress corrosion resistance can be used instead of AISI304 or 316.
Medium Alloy Type Duplex Bolts
The representative grade is UNS S31803 (22Cr-5Ni-3Mo-0.15and N), PREN value is 32-33, its corrosion resistance is between AISI 316L and 6% Mo+N austenitic stainless steel.
High Alloy Type Duplex Bolts
Generally containing 25% Cr, but also contains molybdenum and nitrogen, some also contain copper and tungsten, the standard grade UNSS32550 (25Cr-6Ni-3Mo-2Cu-0.2N), PREN value of 38-39, the corrosion resistance of this type of steel is higher than that of the duplex stainless steel 22% Cr.
Super Duplex Stainless Steel Type
Containing high molybdenum and nitrogen, standard grade UNS S32750 (25Cr-7Ni-3.7Mo-0.3N), some also contain tungsten and copper. PREN value is greater than 40, can be applied to harsh media conditions, has good corrosion resistance and mechanical properties, comparable with super austenitic stainless steel.
Difference Between Duplex Bolts 2205 and Super Dulex Bolts 2507
The main differences between duplex steel 2205 and 2507 bolts are their chemical composition, mechanical properties and corrosion resistance.
Chemical Composition
2205 duplex steel consists mainly of 22% chromium, 3% molybdenum, 5-6% nickel and 0.15-0.30% nitrogen
2507 duplex steel, on the other hand, includes a higher 25% chromium, 4.5% molybdenum, 7-9% nickel and 0.14-0.20% nitrogen
Mechanical Properties
2205 (S31803) bolts have a tensile strength greater than 620 MPa, yield strength greater than 450 MPa, elongation greater than 25%, and hardness HB greater than 290
2507 Duplex steel bolts with tensile strength greater than 800MPa, yield strength greater than 550MPa, elongation greater than 20%. Hardness HB more than 310.
Corrosion Resistance
2205 duplex steel bolts have excellent corrosion resistance and can be successfully used as an alternative to 300 series stainless steel screws, especially in a variety of corrosive media, such as acids, alkalis, salt applications, such as oil and gas, chemical, brewing industry in the pumps, valves, and piping systems in the fastening and connection
The corrosion resistance of 2507 duplex steel bolts is even more outstanding, especially in chlorine-containing media, and its resistance to chloride stress corrosion is about twice that of 2205.
These characteristics make the 2507 duplex steel bolts better suited in certain demanding application scenarios, such as in corrosive environments and high loads at high temperatures.
2507 super duplex bolts are used in the Oil and gas industry; offshore oil platforms (heat exchanger tubes, water treatment, and supply systems, fire protection systems, sprinkler systems, stabilized water systems); petrochemical equipment; desalination (desalination) equipment and equipment (high-pressure tubes, seawater pipes)
We produce 2205, s31803, and 2507 bolts of various standards, as well as duplex nuts and spacers. The dimensions of the duplex fasteners are in accordance with the standards. All duplex materials are produced by large manufacturers and tested by PMI with EN 10204 3.1 certificate.
Contact the Experts
- Ding Fasteners
- N0.52 Qinfen Rd, Haiyan Zhejiang China
- [email protected]
- +86-573-86221432