UNS N08020 / Incoloy® Alloy 20 Special Alloys For Medical Melting Range 2520 - 2600℉

Corrosion resistant alloy 20, UNS N08020, Incoloy® alloy 20, VDM® alloy 20, ATI 20 for processing of pharmaceuticals

PRODUCT

Corrosion resistant alloy 20 for processing of pharmaceuticals and medical devices.

EQUIVALENT DESIGNATION

UNS N08020, NS143, Incoloy® alloy 20, VDM® alloy 20 (Nicrofer 3620Nb), ATI 20^TM, W.Nr. 2.4660, NiCr20CuMo, NAS 335X, FeNi35Cr20Cu4Mo2

PRODUCT FORM

Alloy 20 standard product forms include pipe, tube, sheet, strip, plate, round bar, flat bar, forging stock, hexagon and wire.

Alloy 20 is normally used in the annealed condition.

OVERVIEW

Alloy 20 (UNS N08020) is an iron-based, low carbon, niobium stabilized superaustenitic Ni-Fe-Cr alloy with alloying addition of copper and molybdenum.

Alloy 20 has excellent corrosion resistance in chemical environments containing sulfuric acid, and useful resistance to environments containing chlorides, nitric acid, and phosphoric acid. Alloy 20 has essentially the same resistance to aqueous corrosion as those for alloy 825.

APPLICATION

Alloy 20 is used in a wide variety of applications up to temperatures of approximately 500℃(930℉).

Typical applications are:

Equipment for the manufacture of sulphuric acid and for processes based on sulphuric acid

Extraction columns in the production of amines and the processing of pharmaceuticals

Production of plastics and synthetic fibres

Equipment for food processing to protect against contamination

CHEMICAL COMPOSITION (wt%):

Table 1

PHYSICAL PROPERTY

Density: 8.08g/cm³

Melting range: 1380-1420℃ (2520-2600℉)

CORROSION RESISTANCE

Alloy 20 is characterized by:

Excellent resistance to sulphuric and phosphoric acids

Good resistance to intergranular corrosion

Very good resistance to chloride-ion induced stress-corro-sion cracking

Good resistance to pitting and crevice corrosion

Resistance to sulfuric acid is particularly exceptional but the alloy shows useful resistance in phosphoric acid, nitric acid as well as in chloride environments. Alloy 20 is an excellent option when chloride stress corrosion cracking is an issue and resists pitting and crevice corrosion.

General corrosion

General corrosion is defined as corrosive attack dominated by uniform thinning that proceeds without appreciable localized attack. The general corrosion of stainless steel, and alloys like alloy 20, in many environments, is under 0.001" (0.0254mm) per year; and it is the only form of corrosion occurring. The level of chromium and molybdenum in the alloy 20 provides good resistance to organic acids, but not to the level of high molybdenum alloys like AL-6XN^® alloy (UNS N08367). The level of nickel and copper gives the alloy 20 useful resistance to reducing acids.

Pitting / crevice corrosion

Alloy 20 is comparable to Type 316 in resistance to chloride pitting and crevice corrosion, based on comparable chromium and molybdenum levels in both alloys. In severe chloride pitting and crevice corrosion environments, AL -6XN^® or AL 29-4C^® alloys are better choices. The following data illustrate crevice corrosion resistance of alloy 20 versus other stainless steels.

MECHANICAL PROPERTIES

Alloy 20 is characterized by good mechanical properties at both ambient and elevated temperatures, up to approximately 500℃(930℉).

Table 2 typical room temperature mechanical properties^*, in stabilized annealed condition

* According to applicable ASTM specifications.

Figure 1 High temperature mechanical properties.

HEATING

It is very important that the workpiece be clean and free from any contaminant before and during heating.

Electric furnaces are desirable due to close control of temperature and freedom from contamination. Gas-fired furnaces are acceptable if impurities are at low levels.

The furnace atmosphere should be neutral to slightly oxidising and must not fluctuate between oxidising and reducing. Flame impingement on the metal must be avoided.

During any heating operation, the precautions outlined earlier regarding cleanliness must be observed.

HOT FORMING

Alloy 20 can be formed by either hot-working or cold-working using traditional methods. The material shall be hot worked in the range of 1650-2100℉(900-1150℃), with careful temperature control insuring that the material not fall below 1800°F prior to forging. The final hot-working temperature must not exceed 950℃ (1740℉). Cooling should be by water quenching or as fast as possible.

HARDENING

Alloy 20 is a fully stable austenitic alloy and cannot be hardened by heat treatment. The alloy can be hardened only by cold-working.

COLD WORKING

Cold working should be carried out on annealed material. Alloy 20 has a work-hardening rate similar to that of austenitic stainless steel and the forming equipment must be adapted accordingly.

When cold working is performed, interstage annealing may become necessary.

After cold reductions of more than 15 %, a final stabilising anneal is required before use.

MACHINING

Alloy should be machined in annealed condition. The alloy’s high work-hardening rate should be considered, i.e. only low surface cutting speeds are possible compared with low-alloy standard austenitic stainless steel. Tools should be engaged at all times. Heavy feeds are important in getting below the work-hardened ‘skin’.

JOINING

The weldability of alloy 20 is excellent. Joining can be performed by all the conventional welding processes.

Welding alloy 20 is commonly performed via, GTAW (TIG), GMAW (MIG), Plasma, PHW, SMAW, as well as submerged arc welding (SAW). Pulsed arc welding is the preferred technique, 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.

STANDARD SPECIFICATION

The American society of mechanical engineers has approved the use of N08020 alloy in the construction of welded unfired pressure vessels in the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1; Section VIII, Division 2 and also in Section III, Class 2 and 3. Welded products are covered in American Welding Society 5.4 and 5.9 specifications. The AWS specifications for matching filler are E320-15 and 16.

Rod, Bar, Wire and Forging Stock

ASTM B471 / ASME SB471 Round spring wire

ASTM B462 / ASME SB462 Forged pipe flanges, fittings, valves and parts

ASTM B472 / ASME SB472 Billets and bars for reforging

ASTM B473 / ASME SB 473 Bar and wire

ASTM B475 / ASME SB475 Weaving wire

ISO 9723 Nickel and Nickel alloy bars

ISO 9724 Nickel and Nickel alloy wire and drawing stock

ISO 9725 Nickel and Nickel alloy forgings

DIN 17752 / DIN 17753 / DIN 17754

Plate, Sheet and Strip

ASTM A240 / ASME SA240 Plate, sheet and strip

ASTM A480 / ASME SA480 Plate, sheet and strip

ASTM B463 / ASME SB463 Plate, sheet and strip

ASTM B906 / ASME SB906 Plate, sheet and strip

ISO 6208 Plate, sheet and strip

DIN 17750 Plate, sheet and strip

Pipe and Tube

ASTM B729 / ASME SB729 Seamless pipe and tube

ASTM B829 / ASME SB829 Seamless pipe and tube

ASTM B468 / ASME SB468 Welded tubes

ASTM B751 / ASME SB751 Welded tube

ASTM B464 / ASME SB464 Welded pipe

ASTM B775 / ASME SB775 Welded pipe

ASTM B 474/ ASME SB474 Electric fusion welded pipe

ISO 6207 Seamless tube

DIN 17751 Tube properties

Other

ASTM B366 / ASME SB366 Factory made wrought nickel and nickel alloy welding fittings

DIN 17744 Wrought Ni-Cr-Mo alloy: Chemical composition

COMPETITIVE ADVANTAGE:

(1) More than 50 years experience of research and develop in high temperature alloy, corrosion resistance alloy, precision alloy, refractory alloy, rare metal and precious metal material and products.
(2) 6 state key laboratories and calibration center.
(3) Hundreds of patent technologies.

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