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Alloy 20 Socket Head Cap Screws

Alloy 20 Socket Head Cap Screws, 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) Socket Head Cap Screws 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 Socket Head Cap Screws 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.

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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 Socket Head Cap Screws
SKU: 0

Specialist in Alloy 20 Socket Head Cap Screws · Metric · Inch · Custom

Alloy 20 Socket Head Cap Screws: High-Strength Corrosion-Resistant Allen Screws for Critical Applications

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

RAYCHIN LIMITED is a recognized expert in Alloy 20 socket head cap screws — from Alloy 20 metric socket head cap screws, Alloy 20 inch socket head cap screws, Alloy 20 Allen screws 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 socket head cap screws in sulfuric acid service, phosphoric acid handling, heat exchangers, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment requiring high clamping force and corrosion resistance. 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 socket head cap screws manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS standards. Engineered for extreme environments where corrosion resistance and high strength are critical. Alloy 20 socket head cap screws are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 Socket Head Cap ScrewsAlloy 20 Socket Cap ScrewsAlloy 20 Allen ScrewsAlloy 20 Hex Socket ScrewsUNS N08020 Socket Head Cap Screws2.4660 Socket Head Cap Screws20Cb-3 Socket Head ScrewsCarpenter 20 Socket Head ScrewsIncoloy 20 Socket Head Cap ScrewsASTM B473 Socket Head ScrewsNACE MR0175 Socket Head Cap ScrewsDIN 912 Alloy 20 ScrewsISO 4762 Alloy 20 ScrewsASME B18.3 Alloy 20 Socket Screwssulfuric acid resistant socket screwscorrosion resistant allen screwschemical processing socket screwssour service socket head cap screws

Complete Range of Alloy 20 Socket Head Cap Screws – Configurations

Metric Socket Head Cap Screws (DIN 912 / ISO 4762)

Alloy 20 metric socket head cap screws manufactured to DIN 912 and ISO 4762 standards. Features a cylindrical head with hex socket drive, providing high clamping force and clean appearance. The controlled fillet under the head reduces stress concentration and improves fatigue life. Precision rolled threads for superior strength and corrosion resistance. Ideal for high-temperature corrosive applications up to 538°C. Available in sizes from M3 to M36 in various lengths. Supplied in solution annealed condition per ASTM B473. Suitable for chemical processing, pharmaceutical, and food processing equipment requiring reliable, corrosion-resistant fasteners.

Inch Socket Head Cap Screws (ASME B18.3)

Alloy 20 inch socket head cap screws manufactured to ASME B18.3 standards. Features a cylindrical head with hex socket drive, designed for American standard applications. Precision rolled UNC, UNF, and UNJF-3A threads for superior fatigue resistance. Available in sizes from #0 to 1" in various lengths. Supplied with passivated finish per ASTM A967. Ideal for oil & gas, marine, and industrial applications requiring NACE MR0175 compliance. Also available in low head and button head configurations.

Aerospace & Custom Socket Head Cap Screws

Alloy 20 aerospace socket head cap screws manufactured to NAS1351, NAS1352, and MS16995 standards. Need a special head configuration, unusual thread size, or custom drive for your corrosive application? RAYCHIN engineers work with you to produce custom Alloy 20 socket head cap screws to your drawing. Options include extra-long lengths, reduced head height, and special thread classes. Expert heat treatment (solution annealed at 1030-1120°C) ensures optimum corrosion resistance. Manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN, KS standards.

Key Benefits of Alloy 20 Socket Head Cap Screws

Exceptional Sulfuric Acid Resistance

Superior resistance to sulfuric acid of all concentrations up to elevated temperatures. The nickel-copper-molybdenum combination provides outstanding performance in reducing environments where standard stainless steel screws would fail rapidly. Corrosion rates typically below 0.5 mm/year across most concentrations.

High Clamping Force Design

The cylindrical head with hex socket drive allows for higher tightening torques compared to external drive fasteners. Controlled fillet under head reduces stress concentration and improves fatigue life in cyclic loading applications.

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 socket head cap screws 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 socket screws.

Precision Hex Socket Drive

Deep, accurate hex sockets allow for maximum key engagement and torque transfer without cam-out. Available with standard hex, Torx, and tamper-resistant drive options. Sizes from 1.5mm to 14mm (metric) and 1/16" to 5/8" (inch).

Temperature Versatility

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

Socket Head Cap Screw Design & Standards

Dimensional Standards

Our Alloy 20 socket head cap screws meet or exceed the following specifications:

Metric	DIN 912, ISO 4762
Inch	ASME B18.3
Aerospace (Metric)	NAS1352M
Aerospace (Inch)	NAS1351, NAS1352, MS16995, MS16996
Low Head	DIN 7984, ASME B18.3 (low head)
Button Head	DIN 7380, ISO 7380

Available in UNC, UNF, UNJF-3A, and metric coarse/fine thread configurations.

Drive Options

Hex Socket: Standard drive, sizes from 1.5mm to 14mm (metric) and 1/16" to 5/8" (inch).
Torx Drive: For higher torque transfer and reduced cam-out, sizes T6 through T60.
Tamper-Resistant Torx: With center pin for security applications.
Hexalobular: Per ISO 10664.

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.
Silver Plating: Per AMS 2410 for high-temperature anti-seize.

Manufacturing Standards for Alloy 20 Socket Head Cap Screws

RAYCHIN LIMITED manufactures Alloy 20 socket head cap screws 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 Socket Head Cap Screws

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 socket head cap screws 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 F2281, UNS N08020	Alloy 20 · 20Cb-3 · Carpenter 20 · Incoloy 20
Germany (DIN)	W. Nr. 2.4660, DIN 17744, DIN 912 (socket head cap screws)	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 2470 (socket screws)	NA 20
China (GB)	GB/T 15007, GB/T 1220, GB/T 70.1 (socket head cap screws)	NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)	JIS G4903, JIS G4904, JIS B1176 (socket head cap screws)	NCF 20
ISO	ISO 15156-3 (NACE MR0175), ISO 4762 (socket head cap screws)	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 912 ISO 4762 ASME B18.3 NAS1351

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

Our Alloy 20 socket head cap screws 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 Socket Head Cap Screws (per ASTM B473)

Alloy 20 socket head cap screws 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	—

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	135.9 × 10⁻⁶ ohm-cm (53.5 µohm-in)
Magnetic Permeability	≤ 1.02 (non-magnetic)

Exceptional Corrosion Resistance of Alloy 20 Socket Head Cap Screws

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 socket head cap screws 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. According to isocorrosion diagrams, Alloy 20 is resistant to sulfuric acid of all concentrations up to at least 50°C with a corrosion rate of <0.5 mm/year.

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 Acid Resistance

Excellent resistance to phosphoric acid, including wet process phosphoric acid containing fluoride impurities. Widely used in fertilizer industry applications where socket head cap screws secure agitator blades and mixing equipment.

Chloride Stress Corrosion Cracking (SCC) Resistance

With 32-38% nickel content, Alloy 20 socket head cap screws 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.

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 Socket Head Cap Screws for Corrosive Applications

For critical applications requiring exceptional corrosion resistance and high clamping force, RAYCHIN offers Alloy 20 socket head cap screws manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:

Sulfuric Acid Plants: Heat exchanger covers, pump housings, agitator blade retention, acid cooler access panels, pickling equipment.
Phosphoric Acid Production: Reactor access covers, evaporator inspection ports, heat exchanger heads, mixer blade attachments.
Chemical Processing: Reactor manway covers, distillation column access ports, valve bonnet fasteners, agitator blade screws, instrument connections.
Oil & Gas / Sour Service: NACE MR0175 compliant socket head cap screws for wellhead equipment, valve assemblies, subsea control modules, offshore platform equipment.
Pharmaceutical Manufacturing: Reactor ports, clean room equipment, process piping clamps, sanitary fittings, instrument housings, mixing vessels.
Food Processing: Mixer access covers, tank manways, process equipment guards, sanitary piping systems, conveyor components.
Marine Applications: Instrument enclosures, panel fasteners, offshore platform equipment covers, seawater handling systems.
Standards: DIN 912 (metric), ISO 4762 (metric), ASME B18.3 (inch), NAS1351/NAS1352 (aerospace), MS16995/MS16996 (military).
Thread Classes: 2A, 3A, UNJF-3A (aerospace), 6g, 6H.
Sizes: M3 through M36, #0 through 1".
Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU.

All Alloy 20 socket head cap screws are supplied with full traceability and third-party NDT upon request. Material certifications included.

Why RAYCHIN LIMITED – The Alloy 20 Socket Head Cap Screw 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 socket head cap screws. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our socket head cap screws provide exceptional resistance to sulfuric acid, phosphoric acid, and chloride stress corrosion cracking while maintaining reliable clamping force.

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 socket head cap screws meet applicable ASTM B473, ASME SB473, NACE MR0175, and screw standards including DIN 912, ISO 4762, ASME B18.3, NAS1351.

Precision head forming & socket drive

In-house CNC cold heading and precision socket forming capabilities ensure consistent head dimensions and drive geometry. Precision rolled threads provide superior fatigue life and dimensional accuracy. Deep, accurate hex sockets for maximum key engagement and torque transfer. 100% thread and drive inspection available. Controlled fillet under head for improved fatigue resistance.

Custom solutions

Need a special head configuration, unusual drive, or custom material certification for your corrosive application? Our engineering team works with you to produce custom Alloy 20 socket head cap screws to your drawing. We provide specialized surface treatments, passivation, and NACE MR0175 compliant processing per customer requirements.

Contact the Alloy 20 socket head cap screw experts today

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

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