AISI 664 Forgings Alloy 20 / UNS N08020 seamless rolled rings, flanges, shafts, discs and bars. Open-die forged, solution annealed, certified to ASTM B462.

AISI 664 at a glance

UNS number

N08020

Werkstoff

2.4660

Nominal Ni

35%range 32.0–38.0

Nominal Cr

20%range 19.0–21.0

Density

8.08g/cm³ · 0.292 lb/in³

Tensile, min

551 MPa80 ksi · ASTM B462

Yield 0.2%, min

241 MPa35 ksi · ASTM B462

Elongation, min

30%solution annealed

Chemical composition of AISI 664 (UNS N08020)

The table below gives the ASTM limit range for UNS N08020. Every AISI 664 forging we ship carries a heat analysis certificate, and product analysis can be added on request.

Niobium is added at a minimum of eight times the carbon content, so that carbon is tied up as niobium carbide instead of chromium carbide. That is what stabilises AISI 664 against sensitisation and intergranular corrosion after welding. Melting practice is AOD refining or vacuum induction melting, with vacuum arc or electroslag remelting where the order calls for it.

Mechanical properties of AISI 664 forgings

Values apply to AISI 664 in the solution annealed and water quenched condition at room temperature. Specification minimums govern acceptance. The typical column shows what we normally record on the mill certificate for forged sections.

Heavy sections often test toward the lower end of the typical band, because section size affects the cooling rate through solution annealing. If a property has to be guaranteed at a particular location or depth, say so on the enquiry and we will confirm it before accepting the order.

Physical properties of AISI 664

Published typical values for UNS N08020, given for design guidance. They are not guaranteed properties and do not replace a mill certificate.

Forging and heat treatment of AISI 664

AISI 664 forges without difficulty, but the hot-working window is narrower than for carbon or low-alloy steel and the alloy work-hardens quickly. Our practice on the open-die presses and ring-rolling mills is as follows.

1. Heat uniformly to 1150–1180 °C (2100–2155 °F) and soak until the section has equalised. Do not overheat: above about 1200 °C there is a risk of grain growth and incipient melting.
2. Forge down and finish above 925 °C (1700 °F). Finishing colder than this invites cracking and leaves residual strain that will not fully recrystallise.
3. Reheat as often as the shape needs, rather than pushing one heat too far.
4. Solution anneal at 940–1010 °C (1725–1850 °F), hold for section thickness, then water quench. Slow cooling through 600–900 °C lets carbides and sigma phase precipitate, which costs corrosion resistance.
5. Descale and machine to the drawing. Rigid setups, positive rake, sharp tooling and a heavy feed all help. Dwelling in the cut work-hardens the surface.

AISI 664 forged product forms

We are an open-die forging factory rather than a stockist, so every AISI 664 part listed here is forged to the customer's drawing, or to rough dimensions with machining allowance.

• Seamless rolled rings in AISI 664, ring-rolled radially and axially, for flanges, bearing races, tower and vessel sections
• Forged flanges in AISI 664: weld neck, slip-on, blind, socket weld, threaded, lap joint and long weld neck, ASME B16.5 and B16.47 Class 150 through 2500
• Forged round bars and billets, rough turned, peeled or black
• Forged discs, blanks and tube sheets, including drilled and grooved tube sheets for heat exchangers
• Forged shafts: straight, stepped, eccentric and crankshaft blanks
• Forged sleeves, bushings and hollow bars, trepanned or expanded on the mandrel
• Forged pipe, tube and tube blanks for onward machining
• Forged valve bodies, valve seat rings, valve stems, blocks and nozzles
• Custom open-die forgings made to drawing, in AISI 664 and the other grades listed under nickel alloy forgings

Ranges reflect normal production. Send the drawing to sales@steelforgepieces.com and we will confirm feasibility, forging ratio and finished weight before quoting.

Standards, testing and certification

AISI 664 forgings ship with EN 10204 3.1 mill certificates as standard, and with EN 10204 3.2 certificates witnessed by TUV, SGS, BV, Lloyd's Register or DNV when the order requires it. Testing available on request includes chemical analysis, tensile and impact testing, hardness survey, positive material identification, intergranular corrosion testing to ASTM A262 Practice E, ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388, dye penetrant examination and a dimensional inspection report.

Where AISI 664 forgings are used

AISI 664 is chosen for acid service, and for chloride environments that crack 316L. The uses below are the established ones for the grade.

AISI 664 compared with 316L, Alloy 825 and Alloy 904L

Buyers usually want to know whether AISI 664 is a sufficient step up from 316L, or whether the service needs a higher alloy. The table sets out the main differences.

Composition ranges are nominal and given for orientation. Alloy selection for a particular service should be confirmed against corrosion data for the actual medium, concentration, temperature and aeration.

Frequently asked questions about AISI 664

Related nickel alloy forging grades

Grades most often considered alongside AISI 664, all of which we forge:

• Incoloy 825
• Incoloy 926
• Incoloy 800
• Incoloy 800H
• Hastelloy C-276
• Hastelloy C-22
• Hastelloy G-3
• Alloy 31
• Alloy 59
• Monel 400
• Inconel 625
• Incoloy A-286
• A286
• Incoloy 945
• Incoloy 925