Alloy 20 / UNS N08020 / W.Nr. 2.4660

Alloy 20 (UNS N08020, W. Nr 2.4660) is a nickel-iron-chromium alloy that adds copper and molybdenum. Has good oxidation and reduction of medium corrosion resistance, excellent resistance to local corrosion, and resistance to stress corrosion cracking.

Alloy 20 is very resistant to sulfuric acid and suitable in phosphoric acid, nitric acid, and aqueous salt solutions. It is an excellent option when chloride stress corrosion cracking is an issue, as it resists pitting and crevice corrosion. Caution should be taken in chloride-ion-containing environments because the corrosion rate can increase significantly.

Alloy 20 can be formed by either hot-working or cold-working using traditional methods. Hot-forged material should be heated between 2100°F and 2250°F with careful temperature control, ensuring that the material does not fall below 1800°F before forging. After hot working, anneal the material by heating to 1725°F and 1850°F for a minimum of 30 minutes per inch of thickness, followed by a water quench.

 

When stress relieving is desired, heat to a temperature below 1000°F, followed by water quench after the desired time at temperature has been established. Annealing Alloy 20 should be between 1725°F and 1850°F for 30 minutes at the temperature per inch of thickness. A lower hardness can be obtained by heating to 2100°F, but this may harm the stabilization of the alloy.

 

Welding Alloy 20 is commonly performed via TIG, MIG, as well as submerged arc welding (SAW) using either the matching filler metal, ER320LR for TIG and MIG, and E320LR for SAW. When welding to dissimilar alloys such as 316 or higher alloys such as C276 and Alloy 22, AWS ERNiCrMo-3 can be used for TIG and MIG while using ENiCrMo-3 for SAW.