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Alloy 20 Studs

Alloy 20 Studs, 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) Studs 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 Studs 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 Studs
SKU: 0

Specialist in Alloy 20 Studs · Double-End Studs · Fully Threaded · Tap-End · Customt

Alloy 20 Studs: Corrosion-Resistant Stud Bolts for Flange Connections & Pressure Vessels

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

RAYCHIN LIMITED is a recognized expert in Alloy 20 studs — from Alloy 20 double-end studs, Alloy 20 fully threaded studs, Alloy 20 tap-end studs 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 studs in sulfuric acid service, phosphoric acid handling, heat exchangers, pressure vessels, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment requiring reliable flange connections. Studs, also known as stud bolts, are externally threaded rods without heads, designed to be used with nuts on both ends. They are essential components in ASME B16.5 flange connections, pressure vessel closures, heat exchanger tube sheets, and valve assemblies. 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 studs 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 flange connections are critical. Alloy 20 studs are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 StudsAlloy 20 Stud BoltsAlloy 20 Double-End StudsAlloy 20 Fully Threaded StudsAlloy 20 Tap-End StudsUNS N08020 Studs2.4660 Studs20Cb-3 StudsCarpenter 20 StudsIncoloy 20 StudsASTM B473 StudsNACE MR0175 StudsDIN 938 Alloy 20 StudsDIN 939 Alloy 20 StudsDIN 976 Alloy 20 StudsASME B16.5 Alloy 20 Studssulfuric acid resistant studscorrosion resistant stud boltschemical processing studssour service studspressure vessel studsheat exchanger studs

Complete Range of Alloy 20 Studs – Configurations

Double-End Studs (DIN 938 / DIN 939 / ASME B16.5)

Alloy 20 double-end studs manufactured to DIN 938 (reduced shank), DIN 939 (full body), and ASME B16.5 standards. Features threads on both ends with an unthreaded center section, designed for flange connections and pressure vessel applications. The double-end stud design allows for installation from either end and provides superior vibration resistance. Ideal for high-temperature corrosive applications up to 538°C in refineries, power plants, and chemical processing. Available with or without reduced shank. Supplied with matching Alloy 20 nuts per ASME B16.5 requirements. Sizes from 1/4" to 4" (M6 to M100) in various lengths. NACE MR0175 compliant for sour service applications.

Fully Threaded Studs (DIN 976 / ASME B18.31.2)

Alloy 20 fully threaded studs manufactured to DIN 976, ISO 4014, and ASME B18.31.2 standards. Threaded along the entire length for maximum versatility in applications requiring engagement along the full stud length. Used in heat exchangers, valve assemblies, and structural connections requiring high-temperature capability and corrosion resistance. Precision rolled UNC, UNF, and metric threads for superior fatigue resistance. Available in diameters from 1/4" to 4" (M6 to M100) in custom lengths. Supplied with passivated finish per ASTM A967. Ideal for tube sheet tie rods and general-purpose studding.

Tap-End Studs (DIN 835)

Alloy 20 tap-end studs manufactured to DIN 835 and ASME B18.31.2 standards. Features a shorter thread length on one end (tap end) designed for permanent installation into tapped holes, with a longer thread length on the opposite end (nut end) for nut engagement. Ideal for applications where one side requires permanent fastening while the other side requires removable connections. Commonly used in compressor casings, turbine housings, and equipment where one end is threaded into a blind hole. Available with various thread length ratios to suit specific applications.

Stud Design & Standards

Dimensional Standards

Our Alloy 20 studs meet or exceed the following specifications:

Double-End (Metric)	DIN 938 (reduced shank), DIN 939 (full body)
Double-End (Inch)	ASME B16.5, ASME B18.31.2
Fully Threaded (Metric)	DIN 976, ISO 4014
Fully Threaded (Inch)	ASME B18.31.2
Tap-End (Metric)	DIN 835
Tap-End (Inch)	ASME B18.31.2

Available in UNC, UNF, and metric coarse/fine thread configurations.

Thread Classes & Finishes

Thread Classes: 2A, 3A, 6g, 6H
Passivated: Per ASTM A967 for maximum corrosion resistance
Electropolished: For clean room and pharmaceutical applications
PTFE Coated: For anti-galling and lubricity
Silver Plating: Per AMS 2410 for high-temperature anti-seize

Typical Applications

ASME B16.5 flange connections
Pressure vessel closures
Heat exchanger tube sheets
Valve bonnet assemblies
Compressor casings
Turbine housings
Pipe supports
API 6A wellhead equipment

Key Benefits of Alloy 20 Studs

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. Offers good resistance to stress-corrosion cracking in boiling sulfuric acid at 20-40% concentration, as well as general sulfuric acid resistance. Corrosion rates typically below 0.5 mm/year across most concentrations.

Flange Connection Design

Double-end studs are the preferred fastener for ASME B16.5 flange connections, allowing installation from either end and providing superior vibration resistance. Available with reduced shank for flexibility or full body for maximum strength.

Chloride SCC Immunity

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

Multiple Configurations

Available in double-end, fully threaded, and tap-end configurations to suit specific application requirements. Custom thread lengths and end preparations available.

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 Studs

RAYCHIN LIMITED manufactures Alloy 20 studs 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 Studs

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 studs 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 938 (reduced shank studs), DIN 939 (full body studs), DIN 976 (fully threaded studs), DIN 835 (tap-end studs)	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 4882 (studs)	NA 20
China (GB)	GB/T 15007, GB/T 1220, GB/T 3098.6, GB/T 901 (studs)	NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)	JIS G4903, JIS G4904	NCF 20
ISO	ISO 15156-3 (NACE MR0175), ISO 4014 (applicable)	UNS N08020
NACE	NACE MR0175 / ISO 15156	Alloy 20 (qualified for sour service)
API	API 20F, API 6A	Alloy 20

UNS N08020 2.4660 ASTM B473 ASME SB473 NACE MR0175 20Cb-3 Carpenter 20 Incoloy 20 DIN 938 DIN 939 DIN 976 DIN 835 ASME B16.5 ASME B18.31.2

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

Our Alloy 20 studs 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 after welding or thermal processing.

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

Alloy 20 studs 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.

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 Studs

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 studs 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 studs secure flange connections and heat exchanger tube sheets.

Chloride Stress Corrosion Cracking (SCC) Resistance

With 32-38% nickel content, Alloy 20 studs 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 in the as-welded condition, 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 Studs for Critical Applications

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

Pressure Vessels: ASME B16.5 flange studs, manway cover studs, reactor closure studs, autoclave fasteners.
Heat Exchangers: Tube sheet studs, channel cover studs, floating head studs, tie rods.
Chemical Processing: Reactor connections, distillation column flanges, valve bonnet studs, piping flanges.
Sulfuric Acid Plants: Acid cooler flanges, pump connections, heat exchanger flanges, tower connections.
Phosphoric Acid Production: Evaporator flanges, reactor connections, heat exchanger flanges, pipe flanges.
Oil & Gas / Sour Service: NACE MR0175 compliant studs for wellhead equipment, valve assemblies, subsea flanges, API 6A closures.
Power Generation: Flue-gas desulfurization (FGD) systems, boiler connections, turbine casings, pipe flanges.
Pharmaceutical Manufacturing: Reactor flanges, clean room equipment, sanitary piping flanges, vessel connections.
Food Processing: Mixer flanges, tank manways, process equipment connections, sanitary piping flanges.
Marine Applications: Seawater piping flanges, pump connections, valve flanges, offshore platform equipment.
Standards: DIN 938, DIN 939, DIN 976, DIN 835 (metric), ASME B16.5, ASME B18.31.2 (inch).
Thread Classes: 2A, 3A, 6g, 6H.
Sizes: 1/4" through 4", M6 through M100.
Lengths: Custom lengths per ASME B16.5 flange requirements or customer specification.
Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, API 6A, PED 2014/68/EU.

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

Why RAYCHIN LIMITED – The Alloy 20 Stud 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 studs. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our studs provide exceptional resistance to sulfuric acid, phosphoric acid, and chloride stress corrosion cracking while maintaining reliable flange connection integrity.

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 studs meet applicable ASTM B473, ASME SB473, NACE MR0175, API 20F, and stud standards including DIN 938, DIN 939, DIN 976, ASME B16.5.

Precision thread rolling & end finishing

In-house CNC thread rolling and cutting capabilities ensure precise thread geometry and consistent mechanical properties. Precision rolled threads provide superior fatigue life and dimensional accuracy. Chamfered ends for easy nut engagement. Available thread classes up to 3A/6g. 100% thread inspection available.

Custom solutions

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

Contact the Alloy 20 stud experts today

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

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