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
- Torx screw features and benefits
Also known as Carpenter 20 and 20CB-3, Alloy 20 torx screws offer users a combination of nickel, chromium, molybdenum, and copper which provides good general corrosion resistance. Alloy 20 torx 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 was designed specifically to withstand the harsh environment of hot sulfuric acid but also performs well in a variety of other acids. Alloy 20 torx 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.
Alloy 20 torx 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 torx 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
In addition to their corrosion resistance, Alloy 20 torx screws also perform well at moderately high temperatures, with the ability to maintain their mechanical strength up to 1000°F.
Alloy 20 torx screws are stabilized with Columbium to minimize carbide precipitation during welding. In addition it offers intergranular corrosion resistance in the as-welded condition.
• Power plants rely on alloy 20 torx screws for flue-gas desulfurization
• Alloy 20 torx 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.
• Alloy 20 torx screws help solve corrosion issues in food and dye production.
• Manufacturers of plastics and synthetic rubber also utilize alloy 20 fasteners.
Alloy 20 Torx screws are characterized by a 6-point star-shaped pattern, also called a star drive, spined socket or hexalobular (ISO 10664). Where Phillips heads were designed to cause the driver to cam-out (prevent overtightening), Torx screws were designed resist cam-out. This feature allows Alloy 20 Torx screws to provide increased torque as well as better torque transfer between driver and fasteners. This feature also helps to reduce wear on driver bits.
Alloy 20 Torx Screw Advantages
- Resistant to cam out (process by which a screwdriver slips out of the head)
- Alloy 20 Torx screws are more difficult to strip
- Increased tamper resistance as a star driver isn’t as common
- Driver insert is less susceptible to damage when over torqued than Allen head
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 Comparison