Features of Alloy 20

A brief description of Alloy 20

Nickel alloy 20 is a low-carbon, niobium-stabilized austenitic nickel/iron/chromium alloy with additions of molybdenum and copper. It exhibits exceptional corrosion resistance in chemical environments containing phosphoric acid, nitric acid, chlorides and sulfuric acid. It also has good mechanical properties at both ambient and elevated temperatures.

Alloy 20 was designed specifically to withstand sulfuric acid. Its nickel, chromium, molybdenum and copper levels all provide excellent general corrosion resistance. Restricted carbon plus columbium stabilization permits welded fabrications to be used in corrosive environments, normally without post-weld heat treatment. At 33% nickel, Alloy 20 has practical immunity to chloride stress corrosion cracking. This alloy is often chosen to solve SCC problems, which may occur with 316L stainless.

Although originally designed for use in sulfuric acid related industries, Alloy 20 is now a popular choice for a wide variety of industries including the chemical, food, pharmaceutical, and plastics industries. In addition, this superalloy is used in heat exchangers, mixing tanks, metal cleaning and pickling equipment, and piping. Carpenter 20 combines excellent corrosion resistance with elevated mechanical properties and relatively easy fabrication.

Heat Treatment

Alloy 20 can be formed by either hot-working or cold-work using traditional methods. Hot forged material should be heated between 2100°F and 2250°F with careful temperature control insuring that the material not fall below 1800°F prior to 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 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 temperature per inch of thickness. A lower hardness can be obtained by heating to 2100°F but his may have a negative effect on the stabilization of the alloy.

Welding

Alloy 20 can be welded using conventional methods such as gas tungsten arc welding or gas metal arc welding with appropriate precautions taken for preventing intergranular attack or sensitization during welding. When it comes to machining this alloy, machinists should use tools with sharp edges since it tends to work hard quickly due to its higher carbon content than other stainless alloys like 304 stainless steel or 316 stainless steel. It also requires slower cutting speeds than other alloys since the material tends to be tougher than usual due to its higher nickel content making it difficult to machine at normal speeds without breaking the tool edge or stalling the machine spindle motors.

Processing / Hot Forming

Heat uniformly to a starting temperature of 2100-2225°F. Finish forging before the stock drops below 1800ºF. In order to stabilize the material after hot working operations, reheat at 1750-1850ºF for a minimum of ½-hour per one inch of thickness and water quench.

Processing / Cold Forming

Alloy 20 has good cold formability. Bending, drawing and pressing, and other forming operations that occur in the production of fabricated items are readily performed. Alloy 20 can normally be press brake bent over a radius twice the materials thickness. After cold reductions of more than 15%, a final stabilizing annealing is often required.

In conclusion, alloy 20 offers many advantages over other stainless steels due to its superior corrosion resistance against acidic environments like sulfuric acid and phosphoric acid, along with excellent weldability and machinability properties, making it ideal for use in industrial applications that require corrosive protection from hostile conditions like marine environments or industrial plants where hazardous chemicals are present on a regular basis. With proper maintenance and care, this type of stainless steel can last for years without losing any strength or formability, even when exposed to extreme temperatures or harsh environmental conditions, making it one of the most reliable materials for use in industries around the world today.

Features of Alloy 20

Alloy 20 contains nickel-iron-chromium as the base metal. It also contains copper, which increases its corrosion resistance and improves its stress corrosion cracking resistance. Molybdenum helps increase the strength of this alloy, while chromium provides extra corrosion resistance to resist pitting and crevice corrosion in chloride environments. The most common chemical composition of alloy 20 is as follows:

Resistance to Corrosion

Alloy 20 has very good resistance to sulfuric acid. This alloy also shows suitable resistance in phosphoric acid, nitric acid and aqueous salt solutions. Alloy 20 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. One of Alloy 20 most remarkable features is its unparalleled resistance to corrosion. Delving into the alloy’s molecular structure, we uncover the mechanisms that empower Alloy 20 to withstand the harsh environments of chemical compounds, particularly those containing sulfuric acid. Through real-world examples and scientific insights, we illustrate how Alloy 20 stands as a stalwart guardian against the corrosive forces that can compromise other materials.

Application of Alloy 20

Alloy 20 shows outstanding properties these products are applicable in solutions containing sulfuric acid and several others. Alloy 20 sheet plates help various industries such as chemical processing plants, oil refineries, and petrochemical units, marine and submarine operations. Also, these sheet plates of Alloy 20 are useful in pharmaceutical and food processing plants as well. These products help end-use applications such as storage tanks, product mixing tanks, agitators, and pumps. Several industrial parts such as valves, food processing equipment, fasteners, or fittings are alloy 20. Besides, these products apply to a maximum temperature of 1000°F.

The great properties of alloy 20 make it a commonly used product to make products however it was mostly used in an application where sulfuric acid is used. The common applications include:

Food and dye production

Heat exchangers

Tanks

Explosives

Chemical and allied industries

Valves

Pharmaceuticals

Synthetic rubber and plastic manufacturing

Pickling racks

SO2 scrubbers