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Alloy 20 Washers

Alloy 20 Washers, also known as Carpenter 20 and 20CB-3, offers a combination of nickel, chromium, molybdenum, and copper which provides good general corrosion resistance. Alloy 20 (2.4660) Washers are best suited for mid-range corrosion use – better than steel alloys but not at the level of high performance nickel based alloys like Hastelloy C276. Alloy 20 is a nickel alloy that was specifically designed to withstand the harsh environment of hot sulfuric acid but also performs well in a variety of other acids. Alloy 20 Washers are an ideal choice when you don’t need the corrosion resistance power and price-tag of high performance nickel alloys like Hastelloy C276; but you need something that will give you more protection than 316 stainless steel or even a Super Duplex 2507 stainless steel.

RAYCHIN SPECIALTY METALS FASTENERS: BOLTS, NUTS, SCREWS, WASHERS, STUDS, THREADED RODS, U-BOLT, J-BOLTS

STANDARD AND CUSTOMIZED, SMALL BATCH AND LARGE BATCH, IMPERIAL AND METRIC

Mid-range corrosion resistant alloy
Decent mechanical strength to 1000°F
Good sulfuric acid protection at 20% - 40%
Decent stress corrosion cracking, pitting and crevice corrosion resistance in chloride
Resonable general corrosion protection
Good intergranular corrosion resistance in the as-welded condition

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RAYCHIN LIMITED

Name: Alloy 20 Washers
SKU: 0

Specialist in Alloy 20 Washers · Flat Washers · Heavy Washers · Spring Washers · Custom

Alloy 20 Washers: Corrosion-Resistant Flat Washers for Critical Load Distribution

UNS N08020 / W. Nr. 2.4660 / 20Cb-3 / Carpenter 20 / Incoloy 20

RAYCHIN LIMITED is a recognized expert in Alloy 20 washers — from Alloy 20 flat washers, Alloy 20 heavy washers, Alloy 20 spring washers to custom non-standard configurations. Alloy 20 (UNS N08020) is a nickel-iron-chromium superalloy with additions of copper and molybdenum, stabilized with niobium. Also designated as 20Cb-3, Carpenter 20, and Incoloy 20, it maintains exceptional corrosion resistance in aggressive chemical environments up to 538°C (1000°F). This makes it the preferred material for washers in sulfuric acid service, phosphoric acid handling, heat exchangers, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment requiring corrosion-resistant load distribution. Washers are essential components that distribute the load of threaded fasteners, prevent galling, and provide proper bearing surfaces. They are available in various configurations including flat washers (DIN 125, ISO 7089), large area washers (DIN 9021, ISO 7093), and spring washers (DIN 127, DIN 6796). The alloy's high nickel content (32-38%) provides immunity to chloride stress corrosion cracking, while copper and molybdenum additions enhance resistance to reducing acids. Our portfolio includes washers manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS standards. Engineered for extreme environments where corrosion resistance and reliable load distribution are critical. Alloy 20 washers are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 WashersAlloy 20 Flat WashersAlloy 20 Heavy WashersAlloy 20 Spring WashersAlloy 20 Belleville WashersAlloy 20 Lock WashersUNS N08020 Washers2.4660 Washers20Cb-3 WashersCarpenter 20 WashersIncoloy 20 WashersASTM B473 WashersNACE MR0175 WashersDIN 125 Alloy 20 WashersDIN 9021 Alloy 20 WashersISO 7089 Alloy 20 WashersISO 7093 Alloy 20 WashersASME B18.22.1 Alloy 20 Washerssulfuric acid resistant washerscorrosion resistant flat washerschemical processing washerssour service washers

Complete Range of Alloy 20 Washers – Configurations

Flat Washers (DIN 125 / ISO 7089 / ASME B18.22.1)

Alloy 20 flat washers manufactured to DIN 125, ISO 7089, ISO 7090 (chamfered), and ASME B18.22.1 standards. Available in narrow series (Type A) for general applications. Precision stamped or machined from solution annealed Alloy 20, these washers provide uniform load distribution under bolt heads and nuts. Ideal for high-temperature corrosive applications up to 538°C in pressure vessels, flange connections, and structural assemblies. Available in sizes from #0 to 4" (M1.6 to M100) with various thickness options. Supplied with deburred edges and passivated finish per ASTM A967.

Large Area Washers (DIN 9021 / ISO 7093)

Alloy 20 large area washers manufactured to DIN 9021 and ISO 7093 standards. Features a larger outside diameter compared to standard flat washers, providing increased bearing area for soft materials or oversized holes. Essential for applications where the substrate material requires additional load distribution. Ideal for use with Alloy 20 hex bolts and studs in corrosive environments. Available in sizes from M3 to M100 (metric) and #4 to 4" (inch). Supplied with passivated finish per ASTM A967. Suitable for heat exchanger flanges, vessel connections, and pump assemblies.

Heavy & Spring Washers (DIN 6796 / DIN 127)

Alloy 20 heavy washers (ASME B18.22.1 Type B heavy series) and Alloy 20 spring washers (DIN 6796 Belleville, DIN 127 split lock) provide additional functionality. Heavy washers offer increased thickness for high-pressure applications. Spring washers provide controlled spring force to maintain clamp load during thermal cycling and vibration. Ideal for high-temperature applications where bolt relaxation must be compensated. Available in various load ratings and deflection characteristics. Custom configurations available.

Washer Design & Standards

Dimensional Standards

Our Alloy 20 washers meet or exceed the following specifications:

Metric Flat (Narrow)	DIN 125, ISO 7089, ISO 7090
Metric Flat (Wide)	DIN 9021, ISO 7093
Inch Flat	ASME B18.22.1 Type A
Inch Heavy	ASME B18.22.1 Type B
Spring Washers	DIN 127, DIN 6796, ASME B18.21.1
Aerospace	NASM45305, MS27183

Available in inch and metric sizes from #0 to 4" (M1.6 to M100).

Washer Types

Flat Washers (Type A): Narrow series for general use
Flat Washers (Type B): Wide series for increased bearing area
Chamfered Washers: ISO 7090, rounded edges
Heavy Washers: Extra thickness for high loads
Split Lock Washers: DIN 127, for vibration resistance
Belleville Washers: DIN 6796, conical spring washers

Surface Finish Options

Passivated: Per ASTM A967 for maximum corrosion resistance
Electropolished: For clean room and pharmaceutical applications
PTFE Coated: For anti-galling and lubricity
As-Formed: Clean, deburred edges

Key Benefits of Alloy 20 Washers

Exceptional Sulfuric Acid Resistance

Alloy 20 was specifically developed for sulfuric acid service and has become the industry standard for fasteners in aggressive chemical environments. Washers provide the same corrosion resistance as Alloy 20 bolts and studs, ensuring complete corrosion protection in bolted assemblies.

Load Distribution

Proper washer selection prevents galling, distributes bolt preload evenly, and protects the surface finish of mating components. Essential for maintaining joint integrity in corrosive environments.

Chloride SCC Immunity

With 32-38% nickel content, Alloy 20 offers practical immunity to chloride stress corrosion cracking, making washers ideal for marine and brackish water applications where 304/316 washers would fail.

Sour Service Approved

NACE MR0175 / ISO 15156 qualified for H₂S environments. Suitable for wellhead equipment, valve assemblies, and subsea connections in oil and gas applications requiring corrosion-resistant washers.

Multiple Configurations

Available in flat, heavy, spring, and custom configurations to suit specific application requirements. Custom sizes and thicknesses available for unique applications.

Temperature Versatility

Maintains useful mechanical properties up to 538°C (1000°F), suitable for heat exchanger and process equipment applications at elevated temperatures.

Manufacturing Standards for Alloy 20 Washers

RAYCHIN LIMITED manufactures Alloy 20 washers to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.

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International Standards & Global Designations for Alloy 20 Washers

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 washers from material conforming to the following national and international specifications. This ensures full compliance for projects in the Americas, Europe, Asia, and the Middle East.

Country / Region	Standard / Specification	Designation / Grade
USA	ASTM B473 / ASME SB473, ASTM B462, ASTM B463, ASTM F2281, UNS N08020	Alloy 20 · 20Cb-3 · Carpenter 20 · Incoloy 20
Germany (DIN)	W. Nr. 2.4660, DIN 17744, DIN 125 (flat washers), DIN 9021 (large washers), DIN 127 (spring washers)	2.4660 · NiCr20CuMo
Europe (CEN)	EN 10269 (for fasteners), EN 10095	1.4500 (similar designation)
France (NF)	NF A35-572/573	Z2NCDU25-20
UK (BS)	BS 3076, BS 4320 (washers)	NA 20
China (GB)	GB/T 15007, GB/T 1220, GB/T 97.1 (washers), GB/T 848 (small washers), GB/T 93 (spring washers)	NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)	JIS G4903, JIS G4904, JIS B1256 (washers)	NCF 20
ISO	ISO 15156-3 (NACE MR0175), ISO 7089 (flat washers), ISO 7093 (large washers)	UNS N08020
NACE	NACE MR0175 / ISO 15156	Alloy 20 (qualified for sour service)
API	API 20F	Alloy 20

UNS N08020 2.4660 ASTM B473 ASME SB473 NACE MR0175 20Cb-3 Carpenter 20 Incoloy 20 DIN 125 DIN 9021 ISO 7089 ISO 7093 ASME B18.22.1

Chemical Composition (Weight %) – Alloy 20 (UNS N08020 / 2.4660)

Our Alloy 20 washers are produced from melts that strictly conform to the limits below per ASTM B473 / ASME SB473. The high nickel content provides immunity to chloride stress corrosion cracking, while chromium ensures resistance to oxidizing media. Copper and molybdenum provide exceptional resistance to reducing acids such as sulfuric and phosphoric acids. Niobium stabilization prevents intergranular corrosion.

Element	ASTM B473 / ASME SB473 (Range %)	Typical (analysis)
Nickel (Ni)	32.0 – 38.0	34.0
Chromium (Cr)	19.0 – 21.0	20.0
Copper (Cu)	3.0 – 4.0	3.5
Molybdenum (Mo)	2.0 – 3.0	2.5
Niobium + Tantalum (Nb+Ta)	8 x C min – 1.0 max	0.5
Carbon (C)	≤ 0.07	0.03
Manganese (Mn)	≤ 2.00	1.2
Phosphorus (P)	≤ 0.045	0.020
Sulfur (S)	≤ 0.035	0.010
Silicon (Si)	≤ 1.00	0.5
Iron (Fe)	Balance	Balance

Expert note: The nickel content (32-38%) places Alloy 20 in the austenitic superalloy category, providing exceptional resistance to chloride stress corrosion cracking. Copper (3-4%) is the key element for sulfuric acid resistance, while molybdenum (2-3%) enhances pitting resistance. Niobium stabilization prevents chromium carbide precipitation at grain boundaries, maintaining corrosion resistance.

Complete Mechanical Properties of Alloy 20 Washers (per ASTM B473)

Alloy 20 washers are supplied in the solution annealed condition (1030-1120°C followed by rapid quenching). The data below represent minimum requirements per ASTM B473 / ASME SB473 unless otherwise noted. Washer hardness is consistent with the base material properties.

Tensile Requirements – ASTM B473 (Bar & Fastener Stock)

Size Range	Tensile Strength (min)	Yield Strength 0.2% Offset (min)	Elongation (min)	Reduction of Area (min)
All sizes	550 MPa (80 ksi)	240 MPa (35 ksi)	30%	50%

Typical Mechanical Properties (Solution Annealed)

Property	Typical Value	Notes
Ultimate Tensile Strength	620 MPa (90 ksi)	Exceeds minimum requirements
Yield Strength (0.2% Offset)	300 MPa (43.5 ksi)	Exceeds minimum requirements
Elongation	40%	Excellent ductility
Hardness (Brinell)	217 HB max	Typically 150-190 HB
Hardness (Rockwell C)	19 HRC max	Typically 10-15 HRC
Modulus of Elasticity	193 GPa (28,000 ksi)	At room temperature
Poisson's Ratio	0.31	—
Electrical Resistivity (RT)	651 ohm-cir mil/ft	—

For NACE MR0175 / API 20F sour service applications, maximum hardness of 35 HRC is easily met (Alloy 20 typically below 20 HRC in annealed condition).

Elevated Temperature Mechanical Properties

Alloy 20 maintains useful mechanical properties at elevated temperatures up to approximately 538°C (1000°F), suitable for heat exchanger and process equipment applications.

Temperature	Yield Strength (typical)	Tensile Strength (typical)	Retention (%)
Room Temperature (20°C)	300 MPa	620 MPa	100%
100°C (212°F)	275 MPa	590 MPa	90-95%
200°C (392°F)	260 MPa	570 MPa	85-90%
300°C (572°F)	250 MPa	550 MPa	80-85%
400°C (752°F)	240 MPa	530 MPa	75-80%
500°C (932°F)	230 MPa	500 MPa	70-75%
538°C (1000°F)	220 MPa	480 MPa	65-70%

Note: For service above 538°C, nickel-based alloys such as Inconel 625 or 718 are recommended.

Physical Properties

Property	Value
Density	8.08 g/cm³ (0.292 lb/in³)
Melting Point	1357 – 1430°C (2475 – 2606°F)
Thermal Expansion Coefficient (20-100°C)	14.7 x 10⁻⁶ /°C (8.2 µin/in-°F)
Thermal Conductivity (20°C)	12.3 W/m·K (85 Btu-in/ft²-hr-°F)
Specific Heat Capacity	0.45 J/g·°C
Electrical Resistivity (RT)	135.9 × 10⁻⁶ ohm-cm (53.5 µohm-in)
Magnetic Permeability	≤ 1.02 (non-magnetic)

Exceptional Corrosion Resistance of Alloy 20 Washers

Alloy 20 was originally developed for sulfuric acid service and has become the industry standard for fasteners in aggressive chemical environments. The combination of nickel, chromium, copper, and molybdenum provides outstanding resistance to both oxidizing and reducing acids.

Sulfuric Acid Resistance

Alloy 20 washers offer exceptional resistance to sulfuric acid across a wide range of concentrations and temperatures. The copper addition (3-4%) is particularly beneficial for sulfuric acid environments. Alloy 20 offers good resistance to stress-corrosion cracking in boiling sulfuric acid at 20-40% concentration, as well as general sulfuric acid resistance.

Concentration	Temperature	Corrosion Rate
Up to 50% H₂SO₄	Up to 80°C	< 0.5 mm/year (excellent)
50-80% H₂SO₄	Up to 50°C	< 0.5 mm/year (good)
80-95% H₂SO₄	Room temperature	< 0.5 mm/year (excellent)
All concentrations	Up to 50°C	< 0.5 mm/year (good)

Phosphoric & Nitric Acid Resistance

Excellent resistance to phosphoric acid, including wet process phosphoric acid containing fluoride impurities. Also shows useful resistance to nitric acid. Widely used in fertilizer industry applications where washers are used with Alloy 20 studs and bolts.

Chloride Stress Corrosion Cracking (SCC) Resistance

With 32-38% nickel content, Alloy 20 washers have practical immunity to chloride stress corrosion cracking. This makes them ideal for marine environments, brackish water, and applications where chloride SCC is a concern with 300-series stainless steels.

Pitting and Crevice Corrosion Resistance

The molybdenum addition (2-3%) provides enhanced resistance to pitting and crevice corrosion in chloride-containing media. The Pitting Resistance Equivalent (PRE) is approximately 26-28, providing moderate resistance to localized corrosion in seawater and brine solutions.

Intergranular Corrosion Resistance

Alloy 20 is stabilized with columbium (niobium) to minimize carbide precipitation during welding. This provides excellent intergranular corrosion resistance, maintaining corrosion resistance at grain boundaries.

Resistance to Other Media

Environment	Resistance Level	Notes
Nitric Acid	Good	Chromium provides resistance to oxidizing acids
Hydrochloric Acid	Moderate	Limited resistance at higher concentrations/temperatures
Hydrofluoric Acid	Good	Resistant to all concentrations at room temperature, up to 10% HF at 70°C
Mixed Acids (H₂SO₄ + HNO₃)	Excellent	Widely used in nitration processes
Caustic Solutions	Good	Resistant to caustic soda and potash
Seawater	Good	Moderate resistance to pitting and crevice corrosion
Sour Service (H₂S)	Excellent	Qualified per NACE MR0175/ISO 15156

Special focus: Alloy 20 Washers for Critical Applications

For critical applications requiring exceptional corrosion resistance and reliable load distribution, RAYCHIN offers Alloy 20 washers manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:

Pressure Vessels: Flange washers for ASME B16.5 connections, manway cover washers, reactor closure washers, autoclave fasteners.
Heat Exchangers: Tube sheet washers, channel cover washers, floating head washers, tie rod washers.
Chemical Processing: Reactor connections, distillation column flanges, valve bonnet washers, piping flanges, pump assemblies.
Sulfuric Acid Plants: Acid cooler flanges, pump connections, heat exchanger flanges, tower connections, agitator assemblies.
Phosphoric Acid Production: Evaporator flanges, reactor connections, heat exchanger flanges, pipe flanges, mixer blade washers.
Oil & Gas / Sour Service: NACE MR0175 compliant washers for wellhead equipment, valve assemblies, subsea flanges, API 6A closures.
Pharmaceutical Manufacturing: Reactor flanges, clean room equipment, sanitary piping flanges, vessel connections, mixing tanks.
Food Processing: Mixer flanges, tank manways, process equipment connections, sanitary piping flanges, conveyor components.
Marine Applications: Seawater piping flanges, pump connections, valve flanges, offshore platform equipment, instrument enclosures.
Standards: DIN 125, DIN 9021 (metric), ISO 7089, ISO 7093 (metric), ASME B18.22.1 (inch).
Sizes: #0 through 4", M1.6 through M100.
Thickness: Standard, heavy, and custom thicknesses available.
Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU.

All Alloy 20 washers are supplied with full traceability and third-party NDT upon request. Supplied with matching Alloy 20 bolts, studs, and nuts for complete bolting sets. Material certifications included.

Why RAYCHIN LIMITED – The Alloy 20 Washer Authority

Metallurgical competence

Engineers on staff with deep expertise in nickel-based superalloys. We ensure proper solution annealing (1030-1120°C) for optimal corrosion resistance across all Alloy 20 washers. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our washers provide exceptional resistance to sulfuric acid, phosphoric acid, and chloride stress corrosion cracking.

Global approvals & traceability

Our quality system is ISO 9001:2015 and AS9100D certified; we also comply with NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS. Full material traceability from melt to final packaging (EN 10204 3.1/3.2). Third-party inspections (ABS, DNV, Lloyds) available. All Alloy 20 washers meet applicable ASTM B473, ASME SB473, NACE MR0175, and washer standards including DIN 125, DIN 9021, ISO 7089, ASME B18.22.1.

Precision stamping & finishing

In-house precision stamping and CNC machining capabilities ensure consistent washer dimensions and superior surface finish. Burr-free edges and tight dimensional tolerances. 100% dimensional inspection available. Ultrasonic cleaning and passivation available for critical applications.

Custom solutions

Need a special size, unusual thickness, or custom configuration for your corrosive application? Our engineering team works with you to produce custom Alloy 20 washers to your drawing. We provide specialized surface treatments, passivation, and NACE MR0175 compliant processing per customer requirements.

Contact the Alloy 20 washer experts today

Request a quote for Alloy 20 washers, flat washers, heavy washers, spring washers & custom configurations – any global standard (NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN, KS), any quantity. Inquire about sulfuric acid resistant washers, NACE MR0175 sour service requirements, or high-temperature applications.

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