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Alloy 20 12 Point Screws

Alloy 20 12 Point 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) 12 Point 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 12 Point 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 12 Point Screws
SKU: 0

Specialist in Alloy 20 12 Point Screws · Flange Head · Ferry Cap · Custom

Alloy 20 12 Point Screws: High-Torque Corrosion-Resistant Fasteners for Critical Applications

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

RAYCHIN LIMITED is a recognized expert in Alloy 20 12 point screws — from Alloy 20 12-point flange screws, Alloy 20 ferry cap screws, Alloy 20 12 point head 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). The 12-point head design features two overlapped hexagon shapes, creating 12 points of contact with a flanged underside. This design provides higher torque capability compared to socket head cap screws while eliminating recesses that could trap fluid or debris. The flange distributes pressure where the screw meets the surface, eliminating the need for a separate washer. These screws are also referred to as ferry cap screws or 12-point flange screws. 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 12 point 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 torque capability are critical. Alloy 20 12 point screws are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 12 Point ScrewsAlloy 20 12-Point Flange ScrewsAlloy 20 Ferry Cap ScrewsAlloy 20 12 Point Head ScrewsUNS N08020 12 Point Screws2.4660 12 Point Screws20Cb-3 12 Point ScrewsCarpenter 20 12 Point ScrewsIncoloy 20 12 Point ScrewsASTM B473 12 Point ScrewsNACE MR0175 12 Point Screwssulfuric acid resistant 12 point screwscorrosion resistant 12-point flange screwschemical processing 12 point screwssour service 12 point screwspower generation fastenersaerospace 12 point screwshigh torque corrosion resistant screws

Complete Range of Alloy 20 12 Point Screws – Configurations

Standard 12-Point Flange Screws

Alloy 20 standard 12-point flange screws feature the classic 12-point head design with an integrated flange under the head. The driver uses two overlapped hexagon shapes, creating 12 points of contact for superior torque transfer. The flanged underside eliminates the need for separate washers and distributes clamping load evenly. Ideal for high-temperature corrosive applications up to 538°C where higher torque capability than socket head screws is required. Available in sizes from #10 to 1" (M5 to M24) in various lengths. Supplied in solution annealed condition per ASTM B473. Suitable for chemical processing, power generation, and aerospace applications.

Ferry Cap Screws (External Drive)

Alloy 20 ferry cap screws are a specific type of 12-point screw characterized by their external drive configuration. These screws feature a head that combines 12-point external drive with a smooth, round outer profile. The external drive allows for higher torque application while the smooth exterior prevents debris accumulation. Precision rolled threads for superior strength and corrosion resistance. Available in inch sizes from #10 to 1" and metric sizes from M5 to M24. Ideal for applications in tight spaces where weight savings and high torque are critical. Supplied with passivated finish per ASTM A967.

Aerospace & Custom 12-Point Screws

Alloy 20 aerospace 12-point screws manufactured to NAS and MS standards for critical aerospace applications. 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 12 point 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.

12-Point Screw Design & Advantages

Design Features

12-Point Drive: Two overlapped hexagon shapes create 12 points of contact for superior torque transfer.
Integrated Flange: Flanged underside eliminates need for separate washers and distributes pressure evenly.
Higher Torque Capability: Handles more torque than socket head or hex head screws.
No Fluid Traps: Lack of recess prevents trapping of fluid or debris in corrosive environments.
Space-Efficient: Heads are generally smaller than hex heads, ideal for tight installation spaces.

Application Advantages

Weight Savings: Smaller head size reduces overall weight in critical applications.
Cleanability: Smooth flange design prevents debris accumulation in sanitary applications.
Corrosion Resistance: No recesses means no crevice corrosion initiation sites.
High Preload: Higher torque capability allows greater preload in bolted joints.
Tool Compatibility: Standard 12-point sockets and wrenches are readily available.

Standards & Specifications

Metric	ISO 14581, DIN 34819
Inch	ASME B18.3 (12-point), IFI 115, SAE J1199
Aerospace	NAS178, NAS617, NAS620
Ferry Cap	ASME B18.3 (ferry cap)

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

Key Benefits of Alloy 20 12 Point Screws

Exceptional Sulfuric Acid Resistance

Alloy 20 was specifically designed to withstand hot sulfuric acid 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.

Higher Torque Capability

The 12-point drive provides more points of contact than hex or socket drives, allowing higher installation torque without damaging the fastener. Handles more torque than socket head cap screws of comparable size, enabling higher preload in critical joints.

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 fasteners 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 12-point screws.

Integrated Flange Design

The flanged underside distributes pressure where the screw meets the surface, eliminating the need for separate washers. Reduces parts count and simplifies assembly in corrosive environments.

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 12 Point Screws

RAYCHIN LIMITED manufactures Alloy 20 12 point screws to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.

NASANMSANSIASTMASMESAEAPINACEISODINKSJISGB

International Standards & Global Designations for Alloy 20 12 Point Screws

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 12 point 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 B463, ASTM F2281, UNS N08020	Alloy 20 · 20Cb-3 · Carpenter 20 · Incoloy 20
Germany (DIN)	W. Nr. 2.4660, DIN 17744, DIN 34819 (12-point flange 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	NA 20
China (GB)	GB/T 15007, GB/T 1220, GB/T 3098.6	NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)	JIS G4903, JIS G4904	NCF 20
ISO	ISO 15156-3 (NACE MR0175), ISO 14581 (12-point 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 NAS178 NAS617 NS1403

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

Our Alloy 20 12 point 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. Columbium stabilization ensures intergranular corrosion resistance in the as-welded condition.

Complete Mechanical Properties of Alloy 20 12 Point Screws (per ASTM B473)

Alloy 20 12 point 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	—
Density	8.08 g/cm³ (0.292 lb/in³)	—
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 12 Point 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 12 point 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. 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 12-point screws secure agitator blades and mixing equipment.

Chloride Stress Corrosion Cracking (SCC) Resistance

With 32-38% nickel content, Alloy 20 12 point 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.

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 12 Point Screws for Critical Applications

For critical applications requiring exceptional corrosion resistance and high torque capability, RAYCHIN offers Alloy 20 12 point screws manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:

Power Generation: Flue-gas desulfurization (FGD) systems, heat exchanger connections, turbine components, boiler access panels, steam turbine casings.
Chemical Processing: Reactor manway covers, distillation column access ports, heat exchanger heads, agitator blade screws, mixing tanks, pickling tanks and racks.
Sulfuric Acid Plants: Acid coolers, pump housings, agitator blade retention, piping flanges, acid circulation systems.
Phosphoric Acid Production: Reactor access covers, evaporator inspection ports, heat exchanger heads, mixer blade attachments, piping systems.
Oil & Gas / Sour Service: NACE MR0175 compliant 12-point screws for wellhead equipment, valve assemblies, subsea control modules, offshore platform equipment.
Aerospace: Engine mounts, transmission components, structural fasteners, access panels requiring high strength and corrosion resistance.
Food & Dye Production: Processing equipment, mixing vessels, sanitary piping systems, clean room equipment.
Plastics & Synthetic Rubber: Extruder components, mixer assemblies, reactor connections, processing equipment.
Marine Applications: Instrument enclosures, panel fasteners, offshore platform equipment covers, seawater handling systems.
Standards: ISO 14581 (metric), DIN 34819 (metric), ASME B18.3 (inch), NAS178/NAS617 (aerospace).
Drive Sizes: Standard 12-point socket sizes for both metric and inch configurations.
Thread Classes: 2A, 3A, UNJF-3A, 6g, 6H.
Sizes: #10 through 1", M5 through M24, custom sizes available.
Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU.

All Alloy 20 12 point screws are supplied with full traceability and third-party NDT upon request. Material certifications included.

Why RAYCHIN LIMITED – The Alloy 20 12 Point 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 12 point screws. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our 12-point screws provide exceptional resistance to sulfuric acid, phosphoric acid, and chloride stress corrosion cracking while maintaining high torque capability.

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 12 point screws meet applicable ASTM B473, ASME SB473, NACE MR0175, and aerospace standards including NAS178 and NAS617.

Precision head forming & thread rolling

In-house CNC cold heading and precision thread rolling capabilities ensure consistent head dimensions and 12-point drive geometry. Precision rolled threads provide superior fatigue life and dimensional accuracy. The flanged underside is precisely formed for optimal pressure distribution. 100% thread and drive inspection available.

Custom solutions

Need a special head configuration, unusual thread size, or custom drive for your corrosive application? Our engineering team works with you to produce custom Alloy 20 12 point screws to your drawing. We provide specialized surface treatments, passivation, and NACE MR0175 compliant processing per customer requirements.

Contact the Alloy 20 12 point screw experts today

Request a quote for Alloy 20 12 point screws, 12-point flange screws, ferry cap 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 12-point screws, NACE MR0175 sour service requirements, or high-temperature applications.

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