Duplex & Super Duplex Steel Flat Head Screws

An engineered stainless steel known for its high yield strength & decent corrosion resistance

Flat Head

Duplex 2205 and Super Duplex 2507 stainless steel flat head screws are characterized by their high yield strength, which is twice that of the annealed yield strength of typical austenitic stainless steels, like 304 and 316 stainless steel screws. Because of this, Duplex 2205 and Super Duplex 2507 steel are some of the most common grades of duplex used for flat head screws with Super Duplex 2507 screws being the more corrosion resistant grade of the two.

Super Duplex 2507 flat head screws improved corrosion resistance lends itself well too applications prone to stress-corrosion cracking, crevice corrosion, pitting, erosion and general corrosion. Because of the properties of Duplex and Super Duplex stainless steel screws are often used in chemical processing, petrochemicals, power industry and seawater equipment.

Usage of both Duplex and Super Duplex stainless steel should be limited to temperatures below 570° F as extended elevated temperature exposure can embrittle this material.

The most common grades of Duplex screws are Duplex 2205 and Super Duplex 2507. Gain more insight on these two grades by accessing our Duplex 2205 and Super Duplex 2507 overviews or by contacting our engineering experts.

Resources: Duplex & Super Duplex Torque Specs

Duplex Screw Types: 12 Point Screws, Button Head Cap Screws, Flat Head Screws, Hex Cap Screws, Pan Head Screws, Set Screws, Socket Head Cap Screws, Tamper Resistant Security Screws, Torx Screws

Duplex Flat Head Screw Features and Benefits

Duplex flat head screws are characterized by having a head with a top flat surface (which can feature either a slotted, phillips or allen driver) and bottom that is cone shaped or countersunk. With this design, the head of the screw can align flush or below the surrounding surface having obvious benefits.

Duplex Slotted vs. Phillips Driver 

 Slotted Head Advantages Phillips Head Advantages 
  • Slotted head screws tend to strip less than Philips, especially in harsh environments

  • Slotted heads are typically better in applications where it's going to be unscrewed and re-done periodically, as the head tends to wear less.

  • In dirty environments, a flat head is much easier to clean out
  • Phillips head offers a much stronger joint since it can tolerate more torque.

Countersink Angle

For most flat head screw designs the angle of countersink is usually 82° for UNC and UNF applications however other angles ranging from 60° -120° could be specified. 

Thread Type Normal Flat Head Countersink Angle

UNC / UNF

82°
Aerospace 100°
ISO Metric / Imperial 90°

 

Duplex Screw Grades, Chemistry & Specifications

Duplex Alloy 2205 

Duplex 2205, UNS S32205, is a stainless steel material, whose “Duplex” name is derived from the mixed microstructure which contains roughly 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 Alloy 2205 Specifications: ASME SA 182, ASME SA 240, ASME SA 479, ASME SA 789, ASME SA 789 Section IV Code Case 2603, ASTM A 240, ASTM A 276 Condition A, ASTM A 276 Condition S, ASTM A 479, ASTM A 790, NACE MR0175/ISO 15156, NORSOK MDS D45 Grade F51, UNS S31803, UNS S32205, W. NR./EN 1.4462, Werkstoff 1.4462 Duplex

Duplex 2205 Chemistry

Super Duplex Alloy 2507 

Super Duplex 2507, UNS S32750, is a two-phase stainless steel and is particularly well suited for use in environments such as warm chlorinated seawater and acidic, chloride containing media. It has similiar properties to Duplex 2205 but is more corrosion resistant and performs well in moderately corrosive environments. 

Super Duplex 2507 Specifications:  EN 10216-5, ASTM A789; A790, ASTM A182 ASTM A182, ASTM A815, ASTM A240, EN 10088-2, ASTM A479, EN 10088-3 EN 10088, ISO 15156-3, NACE MR0175, Werkstoff 1.4410 S.Duplex

Super Duplex 2507

Zeron 100 / F55:

Zeron 100, UNS 32760, is commonly know as F55, which is a slight varient of Super Duplex 2507. This alloy is well suited or seawater applications.

Zeron 100/F55 Specifications: ASTM A 182, ASTM A 182 (Grade F55), ASTM A 240, ASTM A 276, ASTM A 473, ASTM A 479, ASTM A 790, ASTM A 815, ASTM A314, NORSOK MDS 055, UNS S32760, W. Nr./EN 1.4501, Werkstoff 1.4501

Zeron 100 Chemistry

  

Mechanical Data

Duplex Stainless Tensile Data

 

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