Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

What is Incoloy 20?

Alloy 20, UNS N08020, is also known as Incoloy 020, Incoloy 20, 20Cb-3, CN7M(castings), or DIN 2.4660. It is a nickel-iron-chromium alloy with additions of copper and molybdenum. It has exceptional corrosion resistance to sulfuric acid, choloride stress-corrosion cracking, nitric acid, and phosphoric acid. Alloy 20 can be readily hot-formed or cold-formed to valves, pipe fittings, flanges, fasteners, pumps, tanks, as well as heat exchanger components. The hot forming temperature should be in the range of 1400-2150°F [760-1175°C]. Usually, the heat treatment of annealing should be conducted at the temperature range of 1800-1850°F [982-1010°C]. Alloy 20 is widely used for the production of gasoline, organic & inorganic chemicals, pharmaceutical processing, and food industry.

Table of Contents hide

astm b366 alloy 20 elbows - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B366 UNS N08020, Incoloy 20 elbows and tees.

The Cr content is usually 19.0-21.0%, and the nickel content is 32.0-38.0%. Incoloy 20 alloy is a nickel-based alloy containing molybdenum and copper, which has good hot and cold working properties. Incoloy 20 is a corrosion-resistant alloy with many excellent properties. It has good resistance to oxidizing and moderately reducing corrosion. It has excellent resistance to stress corrosion cracking and good local corrosion resistance. It is satisfactory in many chemical process media. The corrosion resistance characteristics.

alloy 20 weld neck flanges - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

Alloy 20 weld neck flanges for an Indonesian client.

Chemical Composition Requirements

The Chemical Composition of Alloy 20, %
Nickel 32.0-38.0
Chromiun 19.0-21.0
Copper 3.0-4.0
Molybdenum 2.0-3.0
Iron Balance
Carbon ≤0.07
Niobium+tantalum 8*C-1.0
Managanese ≤2.00
Phosphorus ≤0.045
Sulfur ≤0.035
Silicon ≤1.00

Mechanical Properties of Alloy 20

alloy 20 forged fittings and flanges - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B462 Alloy 20 UNS N08020 forged fittings and forged flanges.

Tensile Strength, min. Yield Strength, min. Elongation, min. Young’s Modulus
Mpa ksi Mpa ksi % 103ksi Gpa
620 90 300 45 40 28 193

Physical Properties of Alloy 20

Density Specific Heat Electrical Resistivity Thermal Conductivity
g/cm3 J/kg.°C µΩ·m W/m.°C
8.08 500 1.08 12.3

Tensile Strength of Alloy 20 at Different Temperatures

Temp °F -20 to 100 200 300 400 500 600 650 700 750 800
T.S1 80.0 80.0 79.2 77.6 77.3 77.3 77.0 76.7 76.3 76.3
T.S2 85.0 85.0 84.1 82.4 82.2 82.1 81.9 81.5 81.1 81.1

  • *TS1(tensile strength of): ASTM B462 UNS N08020 forgings, annealed; ASTM B463 Alloy 20 plate, annealed; ASTM B473 Alloy 20 bar, annealed; ASTM B729 Alloy 20 seamless pipe & tube, annealed; ASTM B464 UNS N08020 welded pipe, annealed; ASTM B468 UNS N08020 welded tube, annealed.
  • *TS2(tensile strength of): ASTM B366 Alloy 20(WP20CB) seamless & welded fittings, annealed.
  • *Temp. refers to metal temperature, not exceeding.
  • *TS1 & TS2: ksi unit.

Yield Strength of Alloy 20 at Different Temperatures

Temp. °F -20 to 100 150 200 250 300 350 400 450
Y.S1 35.0 32.0 30.9 30.2 29.6 29.0 28.4 27.8
Y.S2 40.0 36.6 35.4 34.5 33.8 33.1 32.5 31.8
Temp. °F 500 550 600 650 700 750 800 850
Y.S1 27.3 26.8 26.5 26.2 26.0 25.8 25.2
Y.S2 31.2 30.7 30.3 30.0 29.8 29.4 28.8

  • *YS1(yield strength of):ASTM B462 Alloy 20 forgings, annealed; ASTM B463 UNS N08020 plate, annealed; ASTM B473 UNS N08020 bar, annealed; ASTM B729 Alloy 20 smls. pipe & tube, annealed; ASTM B464 UNS N08020 wld. pipe, annealed; ASTM B468 UNS N08020 wld. tube, annealed; unit: ksi.
  • *YS2(yield strength of):ASTM B366 UNS N08020(WP20CB) smls.& wld. fittings, annealed; unit: ksi.
  • *Temp.: the metal temperature, not exceeding.

Thermal Conductivity & Thermal Diffusivity of Alloy 20

Coefficient of Thermal Conductivity of Alloy 20 (UNS N08020)

Temp. °F 70 100 150 200 250 300 350 400 450 500
TC 6.9 6.9 7.2 7.5 7.8 8.0 8.3 8.6 8.8 9.1
Temp. °F 550 600 650 700 750 800 850 900 950 1000
TC 9.4 9.7 10.0 10.2 10.5 10.8 11.0 11.3 11.6 11.9
  • *TC: the coefficient of thermal conductivity, Btu/hr-ft-°F.
  • *Temp.: metal temperature, not exceeding.

Coefficient of Thermal Diffusivity of Alloy 20 (UNS N08020)

Temp. °F 70 100 150 200 250 300 350 400
TD 0.198 0.198 0.207 0.214 0.222 0.230 0.238 0.246
Temp. °F 450 500 550 600 650 700 750 800
TD 0.255 0.263 0.271 0.278 0.286 0.293 0.300 0.309
  • *TD: the coefficient of thermal diffusivity, ft2/hr.
  • *Temp.: metal temperature, not exceeding.

All tabulated values are in accordance with ASME Boiler & Pressure Vessel Code Section II, Part D.

Modulus of Elasticity of Alloy 20 at Different Temperatures

Temperature -325 -200 -100 70 200 300 400 500 600
Modulus of Elasticity 30.0 29.3 28.8 28.0 27.4 27.0 26.6 26.2 25.8
Temperature 700 800 900 1000 1100 1200 1300 1400 1500
Modulus of Elasticity 25.4 24.9 24.4 23.9 23.4 22.8 22.2 21.6 20.9

  • *The unit for modulus of elasticity is 106 psi; Temperature unit: °F.
  • *All tabular values are in accordance with ASME BPVC Section II Part D Alloy 20 (UNS N08020).
  • *Other physical properties of Alloy 20: poisson’s rate – 0.31; density – 0.291 lb/inch3.

PMI Test on Alloy 20 Butt Welding Fittings

PMI test on Alloy 20 Elbows

pmi test on alloy 20 elbows - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

PMI test on Alloy 20 elbows (ASTM B366 WP20CB), also known as 20Cb3.

The elbow specification: 90° elbow, long radius(L/R), 4″ SCH40 butt welding(BW), ASME B16.9. Materials: ASTM B366 WP20CB (UNS N08020/ 20Cb3/ Alloy 20). The PMI test was conducted by using handheld spectrometer which read: Cr: 19.47%, Mn: 0.91%, Fe: 39.02%, Ni: 34.28%, Cu: 3.6%, Nb: 0.58%, Mo: 2.14%.

PMI test on Alloy 20 Stub Ends

pmi test on alloy 20 stub ends - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

PMI test on ASTM B366 Alloy 20 stub ends(20Cb-3), 4″ long pattern.

The specification of the stub end: ASME B16.9 4″ long pattern. PMI was conducted by using spectrometer which read: Cr: 19.86%, Mn: 0.79%, Fe: 38.50%, Ni: 34.63%, Cu: 3.41%, Nb: 0.57%, Mo: 2.24%. The results conforms to ASME B366 WP20CB (Alloy 20).

Product Forms and Standards

Product Form Standard
Rod, bar and wire ASTM B473, B472, B462
Plate, sheet and strip ASTM A240, A480, B463, B906
Seamless pipe and tube ASTM B729, B829
Welded pipe ASTM B464, B775
Welded tube ASTM B468, B751
Welded fittings ASTM B366
Forged flanges and forged fittings ASTM B462, B472

Application areas of nickel-based alloy incoloy 20 (UNS N08020):

  • Heating pipes, containers, baskets and chains used in sulfuric acid pickling plants.
  • Sea water cooling heat exchanger, marine product pipeline system, acid gas environment pipeline.
  • Heat exchanger, evaporator, washing, dip tube, etc. in phosphoric acid production.
  • Air heat exchanger in petroleum refining.
  • Food engineering, chemical process.
  • Flame retardant alloy for high pressure oxygen application.
  • Heat exchange tubes
  • Pipe fittings
  • Flanges
  • Valves

Alloy 20 Used for Flue-Gas Scrubber

The flue-gas scrubber is widely used for flue gas desulfurization and denitration in residue fluid catalytic cracking unit (RFCCU) of oil refinery, coal-fired power plant, chemical fertilizer plant, and pharmaceutical plant. Considering the corrosive & abrasive environment, Alloy 20 materials shall be selected for the fabrication of accumulator pool, flue-gas distribution baffles, and flue-gas entrance joint. These materials may include ASTM B729 UNS N08020 seamless pipes, ASTM B463 Alloy 20 plates, ASTM B366 Alloy 20 fittings, ASTM B462 Alloy 20 flanges.

flue gas scrubber with alloy 20 baffles fittings - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

Flue gas scrubber with internal gas-distribution baffles made from ASTM B463 Alloy 20 plates.

Alloy 20 for Sulfuric Acid Storage Tank

ss storage tank for h2so4 with alloy 20 fittings at entrance outlet - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

A SS 316 storage tank for sulfuric acids, entrance & outlet fittings/flanges made of Alloy 20 (UNS N08020).

Generally, the most common material for sulfuric acid (with concentration ≥70%) storage tanks is carbon steel due to its low cost. SS 316 can be adopted to avoid iron contamination if required or at low concentrations(≤20%). However, the fittings, flanges, or valves at the feeding entrance and outlets may be made from Alloy 20 which has superior corrosion-resistance & pitting-resistance.

Alloy 20 Used for Hydrometallurgy Facilities

alloy 20 used in hydrometallurgy facilities - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

Alloy 20 materials applied to hydrometallurgy involving sulfuric acid.

The wetted parts of hydrometallurgy facilities involving sulfuric acid shall be made of Alloy 20.

Other Applications

astm b729 alloy 20 tube bundles - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B729 alloy 20 tube bundles for an oil refinery in Mexico.

cast cn7m alloy 20 pump for h2so4 application - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM A351 CN7M, cast Alloy 20 pump for sulfuric acid service.

Alloy 20 Used for Alkylation Process

Recently, Yaang has been supplying a set of Alloy 20 piping materials to an oil-refinery project in Czech. This project involves piping construction of the alkylation process facilities. Due to its exceptional corrosion resistance to sulfuric acid, Alloy 20 (UNS N08020) is selected to displace a section of carbon steels in the original design.

the sulfuric acid alkylation process facility in which alloy 20 materials applied - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

The sulfuric acid alkylation process facilities in which Alloy 20 materials are applied, Lithuania.

Specification Quantity
ASTM B729 Alloy 20 seamless pipes, 6″ SCH40, length=6m 16 pieces
ASTM B366 Alloy 20 fittings (WP20CB), 6″ elbows L/R 90° SCH40 6 pieces
Alloy 20 weld neck flange, 6“ SCH40, 150# 8 pieces
Alloy 20 lap joint stub ends, 4″ long pattern, ASME B16.9. 7 pieces
  • *All the products shall be annealed.

ASTM B473 Alloy 20 Bar

The Alloy 20 bars manufactured to ASTM B473 can be furnished in several types:

  • (1)hot-finished rounds, square, octagons, and hexagons: 0.25″(6.35 mm) and over in diameter or size;
  • (2)hot-finished flats: 0.25″~10″, inclusive, in width, 0.125″(3.175 mm) and over in thickness;
  • (3)cold-finished rounds, squares, octagons, hexagons, and shapes: over 0.5″ in diameter or size;
  • (4)cold-finished flats: 0.375″(9.525 mm) and over in width, 0.125″ and over in thickness.

astm b473 alloy 20 hot rolled bars - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B473 Alloy 20 hot-rolled bars, 36mm x 916mm.

Chemical Composition Requirements

The chemical requirements of ASTM B473 Alloy 20 bar are the same as those of ASTM B564 alloy 20 flanges. Corrosion test in accordance with ASTM A262 practice a shall be performed per heat.

Mechanical Properties of ASTM B473 Alloy 20 Bars

Heat Treatment Diameter Tensile Strength, min. Yield Strength, min. Elongation, min. Reduction of Area
Condition mm ksi MPa ksi MPa in 2″, % min. %
*A All Sizes 80 551 35 241 30.0 50.0
*B ≤2″ 90 620 60 415 15.0 40.0
  • *A: Alloy 20 hot-finished or cold-finished bars, annealed.
  • *B: Annealed Alloy 20 bars, strain-hardened.

Alloy 20 (UNS N08020) Pipes & Tubes

astm b729 seamless alloy 20 pipes 12in std - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B729 seamless Alloy 20 pipes (UNS N08020), 12″ STD PE.

Product Form Standard Specification
Alloy 20 Seamless Pipes & Tubes ASTM B729 UNS N08020
Alloy 20 Welded Pipes ASTM B464 UNS N08020
Alloy 20 Welded Tubes ASTM B468 UNS N08020
  • *All pipes or tubes shall be furnished in stabilize-annealed condition.

Chemical & Mechanical Requirements of Alloy 20 Pipe & Tubes

astm b464 alloy 20 welded pipes 3in s40 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B464 Alloy 20 welded pipes, 3″ SCH40, polished finish.

The chemical & mechanical requirements of Alloy 20 (UNS N08020) is the same as those of alloy 20 flanges & Alloy 20 fittings.

Available Dimensions of Alloy 20 Pipe & Tubes

  • For ASTM B729 Alloy 20 seamless pipes & tubes: 1/2″~16″, SCH10~SCH160.
  • For ASTM B464 Alloy 20 welded pipes: 1/2″~6″, SCH 5S, SCH 10S, SCH 40S, SCH 80S (custom-design welded pipes up to 30″).
  • For ASTM B468 Alloy 20 welded tubes: 1/2″~5″, wall thickness range: 0.38~12.7 mm.
  • The pipe or tube can be furnished in either single random length(SRL), double random length(DRL), or specific cut length.

ASTM B463 Alloy 20 Plate, Sheet, Strip

ASTM B463 Alloy 20 plates, sheets, strips are widely used in the fabrication of pressure vessels, welded pipes or tubes, and other piping components. They can be furnished in various forms which are defined in below table.

Spec. Thickness, t [mm] Width, w [mm]
Alloy 20 cold rolled plate 4.76≤t≤9.52 w>254.0
Alloy 20 hot rolled plate t≥4.76 w>254.0
Alloy 20 plate t≥4.76 w>254.0
Alloy 20 sheet t<4.76 w≥609.6
Alloy 20 strip t<4.76 w<609.6

*The UNS designation is UNS N08020.

astm b463 alloy 20 plates in plywood case - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B463 Alloy 20 plates, hot rolled, packaged in plywood cases.

Chemical Requirements of ASTM B463 Alloy 20 (UNS N08020)

Element Wt, %
Carbon [C] ≤0.07
Manganese [Mn] ≤2.00
Phosphorus [P] ≤0.045
Sulfur [S] ≤0.035
Silicon [Si] ≤1.00
Nickel [Ni] 32.00~38.00
Chromium [Cr] 19.00~21.00
Molybdenum [Mo] 2.00~3.00
Copper [Cu] 3.00~4.00
Niobium+Tantalum [Nb+Ta] 8*Carbon~1.00
Iron remainder
  • *Values shall be based on product analysis.

Mechanical Properties of ASTM B463 Alloy 20 (UNS N08020)

Tensile Strength, min. Yield Strength, min. Elongation in 2″ Hardness, max.
ksi MPa ksi MPa min. % Brinell Rockwell B
80 551 35 241 30.0 217 95
  • *The Alloy 20 plates shall be furnished in stabilize-annealed condition. The annealing temperature shall be 1800~1850°F [982~1010°C].

Available Specification in Stock

hot rolling production line for alloy 20 plate - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

The hot-rolling production line for ASTM B463 plates.

Thickness: 5mm~52mm; Width: 100mm~2000mm; Length: 100mm~6000mm.

ASTM B366 Alloy 20 Fittings

Yaang has committed experience of manufacturing a variety of ASTM B366 Alloy 20 fittings including 90° & 45° elbows, tees, reducers, 180° bends, caps, crosses, lap-joint stub ends, plugs, bushings, street elbows, etc. These fittings has the designation of UNS N08020 and can be used in many corrosive environments.

astm b366 alloy 20 fittings uns 08020 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

Various ASTM B366 Alloy 20 fittings supplied by Yaang.

Product Forms & Dimension Standards of Alloy 20 Fittings

Product Form Dimension Standard
ASME B16.9 Alloy 20 butt welding pipe fittings
ASME B16.11 Alloy 20 forged fittings: threaded or socket welding.
MSS SP 43 Alloy 20 butt welding fittings for low pressure, corrosion resistant applications
MSS SP 95 Alloy 20 swaged nipples and bull plugs
MSS SP 97 Alloy 20 branch outlets: weld outlets, threaded outlet, socket outlets.
  • *The fittings can be either welded or seamless.
  • *UNS N08020 fittings can be furnished in two classes: CR20CB: corrosion-resistant fittings; WP20CB: ASME pressure fittings.

Raw Materials for Alloy 20 Fittings

Raw Material UNS Standard
Pipe or Tube N08020 ASTM B464, B468, B729
Plate, Sheet, or Strip N08020 ASTM B463
Bar or Forging N08020 ASTM B472, B473, B462
  • *The chemical composition & mechanical properties shall conform to corresponding material standard specifications in the table.

Heat Treatment

Alloy 20 fittings shall be annealed at temperature 1700~1850°F [927~1010°C] and quenched at rapid air or water. See more technical specification for alloy 20.

Alloy 20 (UNS N08020) Flanges

Alloy 20 flanges can be readily made from ASTM B462 UNS N08020 forgings or ASTM B463 UNS N08020 plates. They can be furnished in a variety of flange types including weld neck, slip on, threaded, socket welding, blind, lap joint, and LWN, etc. There are 7 rating classes available: Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500, Class 2500.

alloy 20 weld neck flanges 1.5in s40 150 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B462 UNS N08020 (Alloy 20), weld neck flanges, Class 150 RF, 1-1/2″ SCH40.

Chemical Composition

Element Wt, %
Carbon [C] ≤0.07
Manganese [Mn] ≤2.00
Phosphorus [P] ≤0.045
Sulfur [S] ≤0.035
Silicon [Si] ≤1.00
Nickel [Ni] 32.00~38.00
Chromium [Cr] 19.00~21.00
Molybdenum [Mo] 2.00~3.00
Copper [Cu] 3.00~4.00
Niobium+Tantalum [Nb+Ta] 8xCarbon~1
Iron Remainder
  • *The tabulated values are abstracted from ASTM B462 Gr. UNS N08020.

Mechanical Properties

Alloy Tensile Strength, min. Yield Strength, min. Elongation, min. Reduction of Area, min.
ASTM B462 ksi MPa ksi MPa % %
UNS N08020 80 551 35 241 30.0 50.0
  • *All values shall be measured at room temperature.
  • *Alloy 20 flanges shall be supplied in stabilized-annealed condition.

Pressure-Temperature Ratings for Alloy 20(UNS N08020) Flanges

Temp. °C Class 150 Class 300 Class 400 Class 600 Class 900 Class 1500 Class 2500
-29~38 20.0 51.7 68.9 103.4 155.1 258.6 430.9
50 19.5 51.7 68.9 103.4 155.1 258.6 430.9
100 17.7 50.9 67.8 101.7 152.6 254.4 423.9
150 15.8 48.9 65.3 97.9 146.8 244.7 407.8
200 13.8 47.2 62.9 94.3 141.5 235.8 392.9
250 12.1 45.5 60.7 91.0 136.5 227.5 379.2
300 10.2 42.9 57.0 85.7 128.6 214.4 357.1
325 9.3 41.4 55.0 82.6 124.0 206.6 344.3
350 8.4 40.3 53.6 80.4 120.7 201.1 335.3
375 7.4 38.9 51.6 77.6 116.5 194.1 323.2
400 6.5 36.5 48.9 73.3 109.8 183.1 304.9
425 5.5 35.2 46.5 70.0 105.1 175.1 291.6
  • *Working pressures by classes, unit: bar.
asme b16.5 wn flange rf alloy 20 4in 300 s40 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B16.5 weld neck flange, 300# 4″ SCH40 RF, Alloy 20 (UNS N08020) material.

Temp. °F Class 150 Class 300 Class 400 Class 600 Class 900 Class 1500 Class 2500
-20~100 290 750 1000 1500 2250 3750 6250
200 260 740 990 1485 2225 3710 6180
300 230 710 945 1420 2130 3550 5920
400 200 680 910 1365 2045 3410 5680
500 170 655 875 1310 1965 3275 5460
600 140 605 805 1210 1815 3025 5040
650 125 590 785 1175 1765 2940 4905
700 110 570 755 1135 1705 2840 4730
750 95 530 710 1065 1595 2660 4430
800 80 510 675 1015 1525 2540 4230
  • *Working pressures by classes, unit: psig.

Alloy 20 Weld Outlet Class 3000

alloy 20 weld outlet 3000 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

Alloy 20 weld outlet, Class 3000, MSS SP 97.

astm b462 uns n08020 weld outlet 8x1.25 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

ASTM B462 UNS N08020, weld outlet, CL. 3000, 8″x1-1/4″ STD.

Alloy 20 Applicability and Max. Temperature Limits

Alloy 20 is endorsed by relative ASME Boiler & Pressure Vessel Codes (BPVC). A variety of product forms and conditions of Alloy 20 (UNS N08020) are listed in below table which are applicable for corresponding ASME BPVC specifications and temperature limits.

Product Form
& Condition
ASME BPVC Applicability & Maximum Temperature Limits of Alloy 20
I III VIII-1 XII
1 NP 800 800 650
2 NP NP 800 650
3 NP NP 800 650
4 NP 800 800 650
5 NP 800 800 650
6 NP NP 800 650
7 NP NP 800 650
8 NP NP 800 650
9 NP 800 NP NP
10 NP NP 800 650
11 NP NP 800 650
12 NP 800 NP NP
13 NP NP 800 650
14 NP NP 800 650
15 NP NP 800 650

*

  • 1&2: ASTM B462 UNS N08020 forgings, annealed;
  • 3&4: ASTM B463 UNS N08020 plates, annealed;
  • 5&6:ASTM B473 UNS N08020 bars, annealed;
  • 7&8: ASTM B729 Alloy 20 seamless pipe & tube, annealed;
  • 9,10 & 11: ASTM B464 Alloy 20 welded pipe, annealed;
  • 12, 13 & 14: ASTM B468 Alloy 20 welded tube, annealed;
  • 15: ASTM B366 Alloy 20 seamless or welded fitting.
  • I: ASME BPVC Section I Power Boilers;
  • III: ASME BPVC Section III Nuclear Facility Components, Class 2 & 3;
  • VIII-1: ASME BPVC Section VIII Division 1, Pressure Vessels;
  • XII: ASME BPVC Section XII Transport Tanks.
  • NP: not permitted.

Conclusion: Alloy 20 (UNS N08020) materials are not allowed to be used for the construction of power boilers. However, they can be used for the construction of Class 2 & 3 nuclear facility components and transport tanks with maximum temperature limits of 800°F and 650°F respectively.

Allowable Stress of Alloy 20 at Different Temperatures

The table below provides maximum allowable stress values at given temperatures for various Alloy 20 materials. All tabulated values are in accordance with ASME BPVC Section II Part D.

Temp. °F -20 to 100 200 300 400 500 600 650 700 750 800
MAS1, ksi 22.9 22.9 22.6 22.2 22.1 22.1 22.0 21.9 21.8 21.8
MAS2, ksi 22.9 20.6 19.7 18.9 18.2 17.7 17.5 17.4 17.2 16.8
MAS3, ksi 19.4 17.5 16.7 16.1 15.5 15.0 14.9 14.8 14.6 14.3
MAS4, ksi 19.4 19.4 19.2 18.8 18.8 18.8 18.7 18.6 18.5 18.5

  • *Temp.: metal temperature, not exceeding.
  • *MAS1, MAS2, MAS3, MAS4: maximum allowable stress of different product forms/conditions of Alloy 20.
  • *Group MAS1: ASTM B462 UNS N08020 forgings, annealed; ASTM B463 UNS N08020 plate, annealed; ASTM B473 UNS N08020 bar, annealed; ASTM B729 UNS N08020 seamless pipe & tube, annealed; ASTM B464 UNS N08020 welded pipe, annealed; ASTM B468 UNS N08020 welded tube, annealed; ASTM B366 UNS N08020 seamless & welded fittings, annealed,
  • *Group MAS2: ASTM B462 Alloy 20 forgings, annealed; ASTM B463 Alloy 20 plate, annealed; ASTM B473 Alloy 20 bar, annealed; ASTM B729 UNS Alloy 20 seamless pipe & tube, annealed.
  • *Group MAS3: ASTM B464 UNS N08020 welded pipe, annealed; ASTM B468 UNS N08020 welded tube, annealed.
  • *Group MAS4: ASTM B464 Alloy 20 welded pipe, annealed; ASTM B468 Alloy 20 welded tube, annealed.

Incoloy 20 (N08020, Alloy 20) nickel-based alloy phase structure

Incoloy 20 (N08020, Alloy 20) nickel-based alloy is treated at 1120°C for 2h, only TiN nitrides and Cr7C3 type carbides are treated at 870°C by 1500 After long-term aging at ℃, the structure is still Cr7C3 and TiN, indicating that the structure of the alloy is stable. 

Incoloy 20 (N08020, Alloy 20) nickel-based alloy process performance and requirements:

  • 1. Incoloy 20 (N08020, Alloy 20) nickel-based alloy has good hot workability, and the heating temperature for ingot forging is 1110℃~1140℃. The average grain size of the alloy is closely related to the degree of deformation of the forging and the final forging temperature.
  • 2. Incoloy 20 (N08020, Alloy 20) nickel-based alloys have good welding performance and can be connected by various methods such as arc welding, argon arc welding, resistance welding and brazing. Large or complex welding structural parts can be connected after melting. It should be annealed at 870°C for 1h to eliminate welding stress. 
  • 3. Incoloy 20 (N08020, Alloy 20) nickel-based alloys must be machined after heat treatment. Due to the work hardening of the material, it is advisable to use a lower cutting speed and heavy feed than processing low-alloy standard austenitic stainless steel. In order to drive into the underside of the hardened surface.

The Dissimilar Welding of Alloy 20

Alloy 20, also known as 20Cb3, is an iron-based austenitic nickel alloy. It has useful corrosion resistance to oxidizing and medium reducing environments. The alloy also exhibits useful resistance to stress-cracking corrosion and pitting corrosion. Alloy 20 is an ideal piping material for alkylation process in oil refinery. This article introduces the dissimilar welding process of ASTM B729 UNS N08020 (Alloy 20) seamless pipes in SINOPEC’s alkylation facilities in Selangor, Malaysia.

20200801085640 68335 - Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660)

Welding an Alloy 20 seamless pipe to an SS 316 seamless pipe.

Welding Analysis

The issues during the welding of Alloy 20 seamless pipes include:

  • High heat-susceptibility of Alloy 20 which may result in porosity during the welding.
  • The tendency of hot cracking during the welding, as well as intergranular corrosion in welding area.
  • Due to the high nickel content of Alloy 20 and its low flowability in molten status, incomplete fusion may occur.
  • The formation of decarburized zone of pearlite and carburized zone of austenite may cause stress concentration.
  • Residue stress may exist due to the different coefficient of linear thermal expansion between pearlite and austenite of the weld metal.

Actual Chemical Composition & Mechanical Properties

Materials specification: ASTM B729 Alloy 20 (UNS N08020) seamless pipes, 8″ SCH40, bevel ends, length = 6 meters, annealed, 15 pieces. Its actual chemical composition and mechanical properties are listed in below two tables.

Element Content, %
C 0.05
Mn 0.80
Si 0.20
S 0.003
P 0.020
Ni 33.10
Cr 19.70
Cu 3.20
Mo 2.30
Nb+Ta 0.43
Fe Balance
  • *All values are based on actual product analysis. The P Number of Alloy 20 is 45 according to ASME BPVC Section IX.
Tensile Strength, MPa Yield Strength, MPa Elongation, %
595 273 37
  • *The heat number of all Alloy 20 seamless pipes: G8656H.

Welding Methods, Filler Metals, Welding Parameters for Alloy 20

Welding Method Polarity Filler Metal Current Voltage Welding Velocity
Classification Size, mm A V cm/min
GTAW/ TIG DCEP ERNiCrMo-3 Φ2.5 110~160 10~16 5~9
SMAW DCEN ENiCrMo-3 Φ3.2 80~120 19~25 5~8
  • *Welding electrodes of ERNiCrMo-3 or ENiCrMo-3 are selected respectively as the filler metal for Alloy 20 dissimilar welding.
  • *The root pass shall be welded by GTAW/ TIG method; the filler passes & cover passes shall be welded by SMAW method.
  • *The heat input of each pass shall be < 20kJ/cm to prevent Alloy 20 from heat cracking. Interpass temperature shall be < 100°C.

Chemical Composition and Mechanical Properties of Filler Metal

Material C Mn Fe S Si Cu Ni Cr Al Co Mo P
ERNiCrMo-3 0.030 0.31 3.10 0.010 0.41 0.030 61.80 22.20 0.12 8.78 0.010
ENiCrMo-3 0.018 0.48 5.23 0.010 0.33 0.042 60.50 21.30 0.052 8.54 0.006
  • *The filler metals for Alloy 20 welding shall be selected in accordance with AWS A5.14(GTAW) or AWS A5.11(SMAW) respectively.
  • *The UNS designation of AWS A5.14 ERNiCrMo-3 is N06625; the UNS designation of AWS A5.11 ENiCrMo-3 is W86112.
  • *All tabulated values are actually measured.
Classification Tensile Strength, MPa Yield Strength, MPa Elongation, %
ERNiCrMo-3 768 380 43.7
ENiCrMo-3 793 441 35.8

*All values of the mechanical properties are actually measured.

Important Notice for Dissimilar Welding of Alloy 20

Before the dissimilar welding, the bevel ends of the Alloy 20 seamless pipe and SS 316 seamless pipe shall be carefully cleaned. Generally, preheating is not required. However, when the base metal temperature is lower than 15°C, induction heating shall be conducted to avoid air condensing. During the welding, there shall be no appreciable weaving motion.

Variety specifications and supply status of Nickel-based super alloy: Incoloy 20 (UNS N08020/DIN 2.4660):

Variety classification:

Yaang Pipe Industry can produce various specifications of Incoloy20 seamless pipe, Incoloy20 steel plate, Incoloy20 round bar, Incoloy20 forgings, Incoloy20 flangeIncoloy20 pipe fittings, Incoloy20 welded pipe , Incoloy20 steel strip, Incoloy20 wire and supporting welding materials. 

Delivery status:

  • Seamless pipe: solid solution + acid white, length can be set;
  • Plate: solid solution, pickling, trimming;
  • Welded pipe: solid solution acid white + RT% flaw detection;
  • Forging: annealing + car polish; Bars are forged and rolled, surface polished or car polished;
  • Strips are delivered after cold rolling, solid solution soft state, and deoxidized;
  • Wire rods are finely ground in solid solution pickled disk or straight strips, solid solution straight strips Delivery in light state.

Source: China Incoloy 20 Flanges Manufcturer – Yaang Pipe Industry (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

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