Alloy 20 Flat Head Screws
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
Specialist in Alloy 20 Flat Head Screws · 82° · 90° · Metric · Inch · CustomAlloy 20 Flat Head Screws: Corrosion-Resistant Countersunk Screws for Flush-Mount Applications
RAYCHIN LIMITED is a recognized expert in Alloy 20 flat head screws — from Alloy 20 metric flat head cap screws, Alloy 20 inch flat head socket screws, Alloy 20 82° countersunk screws, Alloy 20 90° flat 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 500°C (930°F). This makes it the preferred material for flat head screws in sulfuric acid service, phosphoric acid handling, heat exchangers, pressure vessels, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment where a smooth, flush surface is required. 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 flat head 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 flush mounting are critical. Alloy 20 flat head screws are supplied in solution annealed condition with full traceability and third-party certifications.
Complete Range of Alloy 20 Flat Head Screws – Configurations
Metric Flat Head Screws (DIN 7991 / ISO 10642)
Alloy 20 metric flat head screws manufactured to DIN 7991 and ISO 10642 standards. Features a countersunk head with 90° included angle for metric sizes, designed for flush mounting applications. Precision rolled threads for superior strength and corrosion resistance. Ideal for high-temperature corrosive applications up to 500°C. Available in sizes from M3 to M24 in various lengths. Hex socket drive for positive engagement. Supplied in solution annealed condition per ASTM B473. Suitable for chemical processing, pharmaceutical, and food processing equipment where smooth surfaces and cleanability are essential.
Inch Flat Head Screws (ASME B18.3)
Alloy 20 inch flat head screws manufactured to ASME B18.3 standards. Features a countersunk head with 82° included angle for inch sizes, designed for flush mounting in American standard applications. Precision rolled UNC, UNF, and UNJF-3A threads for superior fatigue resistance. Available in sizes from #4 to 1" in various lengths. Hex socket drive for maximum torque transfer. Supplied with passivated finish per ASTM A967. Ideal for oil & gas, marine, and industrial applications requiring NACE MR0175 compliance.
Custom & Specialty Flat Head Screws
Need a special head angle, unusual thread size, or custom drive for your corrosive application? RAYCHIN engineers work with you to produce custom Alloy 20 flat head screws to your drawing. Options include Torx drive, tamper-resistant drive, custom head angles (100°, 120°, etc.), and extra-long lengths. 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 Flat Head 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.
Flush Mounting Design
The countersunk flat head design allows for complete flush installation, eliminating protruding surfaces. Ideal for applications requiring smooth surfaces, fluid flow optimization, or aesthetic appearance. Available in 82° (inch) and 90° (metric) head angles.
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 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.
Precision 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.
Temperature Versatility
Maintains useful mechanical properties up to 500°C (930°F), suitable for heat exchanger and process equipment applications at elevated temperatures.
Flat Head Screw Design & Standards
Dimensional Standards
Our Alloy 20 flat head screws meet or exceed the following specifications:
Available in UNC, UNF, UNJF-3A, and metric coarse/fine thread configurations.
Drive Options
- Hex Socket: Standard drive, sizes from 1.5mm to 10mm (metric) and 1/16" to 3/8" (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.
- Slotted: Available for certain sizes.
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 Flat Head Screws
RAYCHIN LIMITED manufactures Alloy 20 flat head screws to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.
International Standards & Global Designations for Alloy 20 Flat Head Screws
To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 flat head 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.
UNS N08020 2.4660 ASTM B473 ASME SB473 NACE MR0175 20Cb-3 Carpenter 20 Incoloy 20 DIN 7991 ISO 10642
Chemical Composition (Weight %) – Alloy 20 (UNS N08020 / 2.4660)
Our Alloy 20 flat head 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.
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 Flat Head Screws (per ASTM B473)
Alloy 20 flat head 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)
Typical Mechanical Properties (Solution Annealed)
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 500°C (930°F), suitable for heat exchanger and process equipment applications.
Note: For service above 500°C, nickel-based alloys such as Inconel 625 or 718 are recommended.
Physical Properties
Exceptional Corrosion Resistance of Alloy 20 Flat Head 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 flat head 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 is resistant to sulfuric acid of all concentrations up to at least 50°C with corrosion rates below 0.13 mm/year.
Phosphoric Acid Resistance
Excellent resistance to phosphoric acid, including wet process phosphoric acid containing fluoride impurities. Widely used in fertilizer industry applications.
Chloride Stress Corrosion Cracking (SCC) Resistance
With 32-38% nickel content, Alloy 20 flat head 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
Special focus: Alloy 20 Flat Head Screws for Corrosive Applications Requiring Flush Surfaces
For critical applications requiring both exceptional corrosion resistance and flush mounting, RAYCHIN offers Alloy 20 flat head screws manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:
- Sulfuric Acid Plants: Heat exchanger covers, piping flange connections, pump housings, acid cooler access panels, pickling equipment where smooth surfaces prevent acid entrapment.
- Phosphoric Acid Production: Reactor access covers, evaporator inspection ports, heat exchanger heads, mixer blade attachments requiring flush surfaces.
- Chemical Processing: Reactor manway covers, distillation column access ports, valve bonnet fasteners, agitator blade screws where flush mounting is essential.
- Oil & Gas / Sour Service: NACE MR0175 compliant flat head screws for instrument panels, valve covers, subsea control modules requiring flush surfaces.
- Pharmaceutical Manufacturing: Reactor ports, clean room equipment, process piping clamps, sanitary fittings, instrument housings requiring smooth, cleanable surfaces.
- Food Processing: Mixer access covers, tank manways, process equipment guards, sanitary piping systems where flush surfaces prevent bacterial growth.
- Marine Applications: Instrument enclosures, panel fasteners, offshore platform equipment covers requiring flush mounting.
- Standards: DIN 7991 (metric), ISO 10642 (metric), ASME B18.3 (inch, 82°), NAS562 (aerospace).
- Head Angles: 82° (inch standard), 90° (metric standard), 100° (aerospace), custom angles available.
- 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 flat head screws are supplied with full traceability and third-party NDT upon request. Material certifications included.
Why RAYCHIN LIMITED – The Alloy 20 Flat Head 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 flat head screws. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our screws 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 flat head screws meet applicable ASTM B473, ASME SB473, NACE MR0175, and screw standards including DIN 7991, ISO 10642, ASME B18.3.
Precision head forming & threading
In-house CNC cold heading and precision thread rolling capabilities ensure consistent head angles and thread geometry. Precision rolled threads provide superior fatigue life and dimensional accuracy. Deep, accurate hex sockets for maximum key engagement. 100% thread inspection available. Head angle tolerance ±1° ensures flush seating.
Custom solutions
Need a special head angle, unusual drive, or custom material certification for your corrosive application? Our engineering team works with you to produce custom Alloy 20 flat head screws to your drawing. We provide specialized surface treatments, passivation, and NACE MR0175 compliant processing per customer requirements.
Contact the Alloy 20 flat head screw experts today
Request a quote for Alloy 20 flat head screws, metric flat head screws, inch flat head screws, 82° countersunk screws, 90° flat head 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 screws, NACE MR0175 sour service requirements, or high-temperature applications.
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