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

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.

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 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

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

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

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.

Alloy 20 for Sulfuric Acid Storage Tank

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

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

Other Applications

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.

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.

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

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

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.

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

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.

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.

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.

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 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.

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 flange, Incoloy20 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.)

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