Good Mid-Range Corrosion Resistant Alloy 

• Mid-range corrosion resistant alloy
• Decent mechanical strength to 1000°F
• Alloy 20 chemistry and specifications  
• Alloy 20 sulfric acid performance
• Set screw features and benefits
• Alloy 20 Datasheet

Also known as Carpenter 20 and 20CB-3, Alloy 20 set screws offer users a combination of nickel, chromium, molybdenum, and copper which provides good general corrosion resistance. Alloy 20 set screws are best suited for mid-range corrosion use – better than steel alloys but not at the level of high performance nickel based alloys like Hastelloy C276. Alloy 20 is a nickel alloy that was specifically designed to withstand the harsh environment of hot sulfuric acid but also performs well in a variety of other acids. Alloy 20 set screws are an ideal choice when you don’t need the corrosion resistance power and price-tag of high performance nickel alloys like Hastelloy C276; but you need something that will give you more protection than 316 stainless steel or even a Super Duplex 2507 stainless steel.

Corrosion Resistance
Alloy 20 set screws provide good performance in hot sulfuric acid, specifically they offer good resistance to stress-corrosion cracking in boiling sulfuric acid at specific range of 20% to 40% concentration, as well as general sulfuric acid resistance. Alloy 20 offers solid acid protection and will perform better than Duplex or even Monel, but for high temperature and high concentration acids, you may need to look to Inconel or Hastelloy fasteners. In addition, Alloy 20 set screws also show useful resistance to phosphoric acid and nitric acid.

Key Corrosion Resistant Features:

• Good sulfuric acid protection at 20% - 40%
• Decent stress corrosion cracking, pitting and crevice corrosion resistance in chloride
• Resonable general corrosion protection
• Good intergranular corrosion resistance in the as-welded condition

Mechanical Properties
o  Ultimate tensile strength: 80 ksi
o  Yield strength: 35 ksi
o  Density: 0.292 lb/in.3
o  Electrical Resistivity (RT) 651 ohm-cir mil/ft
o  Elongation: 30%

Temperature
In addition to their corrosion resistance, Alloy 20 set screws also perform well at moderately high temperatures, with the ability to maintain their mechanical strength up to 1000°F.

Welding
Alloy 20 set screws are stabilized with Columbium to minimize carbide precipitation during welding. In addition it offers intergranular corrosion resistance in the as-welded condition.

Applications
o  Power plants rely on alloy 20 set screws for flue-gas desulfurization
o  Alloy 20 set screws are used to connect heat exchangers, mixing tanks, metal cleaning equipment, pickling tanks and racks, and piping in mid-range corrosive chemcial processing environments.
o  Alloy 20 set screws help solve corrosion issues in food and dye production.
o  Manufacturers of plastics and synthetic rubber also utilize alloy 20 fasteners.

Resources: Alloy 20 Torque Specs, Flange Dimensions, Flange Bolting Chart

Alloy 20 Screw Types: 12 Point Screws, Button Head Cap Screws, Flat Head Screws, Hex Head Cap Screws, Pan Head Screws, Set Screws, Socket Head Cap Screws, Tamper Resistant Security Screws, Torx Screws

Alloy 20 Set Screw Features & Benefits

Alloy 20 set screws are unique in that they have no screw head, meaning that they have no protruding part past the threaded shaft. They are thread only and are available with a socket or slotted driver insert at one end. Set screws are used to secure an object within or against another object. Typically they secure a rotating part such as a gear or shaft. Alloy 20 set screws are driven through a threaded hole in the rotating part until it is tight against the inner object, preventing from moving relative to the outer object. Set screws are available with various points depending on the application.

Cup Point 
This is the most commonly used set screw and is identified by a cup-shaped indentation on one end. Alloy 20 cup points are typically used for a quick, semi-permanent or permanent applications where it is acceptable to cut the cup point edge of the screw.

Cone Point
A cone point is easily identifiable by its sharp cone-shaped point – just like an ice cream cone. Alloy 20 cone point set screws deliver the strongest clamping force due to the deep penetration of the point. As a result they are used for permanent assembly.

Flat Point

The cheapest and simplest of the set screw point styles, this screw has a flat surface on the bottom of the screw. This type is used when you need the ability to frequently change parts and require minimal shaft deformation.

Alloy 20 Chemistry & Specifications

Alloy 20 Specifications: UNS N08020, ASME SA240, , ASME SB366, ASME SB462, ASME SB463, ASME SB464,  ASME SB473, ASME SB729, ASTM A240, ASTM B366, ASTM B463, ASTM B464, ASTM B473, ASTM B729, ASTM BB462, ANSI/ASTM A555-79, EN 2.4660, , Werkstoff 2.4660, CN7M, DIN 2.4660

Alloy 20 Sulfuric Acid Performance

Alloy 20 Sulfuric Acid Comparison