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Alloy 20 Torx Screws

Alloy 20 Torx 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) Torx 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 Torx 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.

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 Torx Screws
SKU: 0

Specialist in Alloy 20 Torx Screws · Button Head · Flat Head · Custom

Alloy 20 Torx Screws: Corrosion-Resistant Star Drive Screws for Superior Torque Transfer

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

RAYCHIN LIMITED is a recognized expert in Alloy 20 Torx screws — from Alloy 20 button head Torx screws, Alloy 20 flat head Torx screws, Alloy 20 Torx drive 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 Torx screws in sulfuric acid service, phosphoric acid handling, heat exchangers, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment where superior torque transfer and corrosion resistance are required. The Torx drive (hexalobular per ISO 10664) features a 6-point star-shaped pattern that provides increased torque transfer and resistance to cam-out compared to Phillips or slotted drives. 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 Torx 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 reliable drive engagement are critical. Alloy 20 Torx screws are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 Torx ScrewsAlloy 20 Star Drive ScrewsAlloy 20 Hexalobular ScrewsAlloy 20 Torx Drive ScrewsAlloy 20 Button Head Torx ScrewsAlloy 20 Flat Head Torx ScrewsUNS N08020 Torx Screws2.4660 Torx Screws20Cb-3 Torx ScrewsCarpenter 20 Torx ScrewsIncoloy 20 Torx ScrewsASTM B473 Torx ScrewsNACE MR0175 Torx ScrewsDIN 7380 Alloy 20 ScrewsISO 10664 Torx Drivesulfuric acid resistant Torx screwscorrosion resistant star drive screwschemical processing Torx screwssour service Torx screwstamper resistant Torx screws

Complete Range of Alloy 20 Torx Screws – Configurations

Button Head Torx Screws (DIN 7380 / ISO 7380)

Alloy 20 button head Torx screws manufactured to DIN 7380 and ISO 7380 standards. Features a low-profile domed head with Torx drive, providing a smooth appearance and reduced turbulence in fluid applications. The Torx drive allows for higher installation torque without damaging the recess. 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 M24 (metric) and #4 to 1" (inch). Supplied in solution annealed condition per ASTM B473. Suitable for chemical processing, pharmaceutical, and food processing equipment where aesthetics and cleanability are essential.

Flat Head Torx Screws (DIN 7991 / ISO 10642)

Alloy 20 flat head Torx screws manufactured to DIN 7991, ISO 10642, and ASME B18.3 standards. Features a countersunk head designed to sit flush with the surface for aerodynamic or aesthetic requirements. Available with 82° (inch) or 90° (metric) head angles. Torx drive allows for higher installation torque without damaging the recess. Ideal for aerospace applications, manifold covers, and equipment where flush mounting is essential in corrosive environments. Precision rolled UNC, UNF, and metric threads. Available in sizes from M3 to M24 and #4 to 1".

Tamper-Resistant & Custom Torx Screws

Alloy 20 tamper-resistant Torx screws feature a modified Torx drive with a center pin that prevents standard Torx bits from engaging. Designed for security applications where unauthorized access must be prevented in corrosive environments. Need a special head style, unusual drive configuration, or custom length? RAYCHIN engineers work with you to produce custom Alloy 20 Torx screws to your drawing. Options include Torx Plus drive, combination drives, and custom head configurations. 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 Torx Screws

Superior Torque Transfer

The Torx drive provides more points of contact than other drives, allowing higher installation torque without damaging the recess. Resists cam-out, extends tool life, and provides better torque transfer between driver and fastener.

Exceptional Sulfuric Acid Resistance

Superior resistance to sulfuric acid of all concentrations up to elevated temperatures. Alloy 20 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.

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 Torx 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 Torx screws.

Reduced Tool Wear

The Torx drive design reduces wear on driver bits compared to other drive systems, providing longer tool life and more consistent torque application during assembly.

Temperature Versatility

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

Torx Drive Design & Standards

Dimensional Standards

Our Alloy 20 Torx screws meet or exceed the following specifications:

Button Head Torx	DIN 7380, ISO 7380
Flat Head Torx	DIN 7991, ISO 10642, ASME B18.3
Torx Drive Standard	ISO 10664, ASME B18.3 (Torx)
Tamper-Resistant Torx	Modified per customer specification

Available in UNC, UNF, UNJF-3A, and metric coarse/fine thread configurations. Drive sizes from T6 to T60.

Torx Drive Advantages

Higher Torque Capacity: Up to 30% higher torque than hex socket drives.
Reduced Cam-Out: Eliminates the cam-out problem of Phillips drives.
Extended Tool Life: Longer bit life due to reduced wear.
Better Engagement: Vertical walls transfer torque more efficiently.

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 Torx Screws

RAYCHIN LIMITED manufactures Alloy 20 Torx 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 Torx Screws

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 Torx 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 7380 (button head Torx), DIN 7991 (flat head Torx)	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 70.2 (button head), GB/T 70.3 (flat head)	NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)	JIS G4903, JIS G4904	NCF 20
ISO	ISO 15156-3 (NACE MR0175), ISO 7380 (button head), ISO 10642 (flat head), ISO 10664 (Torx drive)	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 7380 DIN 7991 ISO 7380 ISO 10642 ISO 10664

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

Our Alloy 20 Torx 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 Torx Screws (per ASTM B473)

Alloy 20 Torx 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 Torx 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 Torx 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 Torx screws secure agitator blades and mixing equipment.

Chloride Stress Corrosion Cracking (SCC) Resistance

With 32-38% nickel content, Alloy 20 Torx 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 Torx Screws for Corrosive Applications

For critical applications requiring exceptional corrosion resistance and superior torque transfer, RAYCHIN offers Alloy 20 Torx 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 Torx 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.
Aerospace: Interior panel fasteners, instrument mounting, access panels requiring flush surfaces.
Standards: DIN 7380 (button head Torx), DIN 7991 (flat head Torx), ISO 7380, ISO 10642, ASME B18.3.
Drive Sizes: T6 through T60 available, custom drive configurations per drawing.
Thread Classes: 2A, 3A, UNJF-3A, 6g, 6H.
Sizes: M3 through M24, #4 through 1".
Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU.

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

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

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 Torx screws meet applicable ASTM B473, ASME SB473, NACE MR0175, and screw standards including DIN 7380, DIN 7991, ISO 7380, ISO 10642.

Precision head forming & drive forming

In-house CNC cold heading and precision drive forming capabilities ensure consistent head dimensions and Torx drive geometry. Precision rolled threads provide superior fatigue life and dimensional accuracy. Deep, accurate Torx recesses for positive driver engagement and maximum torque transfer. 100% thread and drive inspection available.

Custom solutions

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

Contact the Alloy 20 Torx screw experts today

Request a quote for Alloy 20 Torx screws, button head Torx screws, flat head Torx screws, star drive 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 Torx screws, NACE MR0175 sour service requirements, or high-temperature applications.

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