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Alloy 20 Fasteners

Alloy 20 Pan Head Screws

Alloy 20 Pan Head 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) Pan Head 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 Pan Head 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.
  • Alloy 20 Pan Head Screws
  • Alloy 20 Pan Head Screws
  • Alloy 20 Pan Head Screws
  • Alloy 20 Pan Head Screws
  • Alloy 20 Pan Head Screws
  • Alloy 20 Pan 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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Alloy 20 Pan Head Screws: Corrosion-Resistant Machine Screws for Versatile Applications

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

RAYCHIN LIMITED is a recognized expert in Alloy 20 pan head screws — from Alloy 20 metric pan head screws, Alloy 20 inch pan head machine screws, Alloy 20 Phillips drive pan head screws, Alloy 20 slotted pan 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 pan head screws in sulfuric acid service, phosphoric acid handling, heat exchangers, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment. 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 pan 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 reliable fastening are critical. Alloy 20 pan head screws are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 Pan Head ScrewsAlloy 20 Machine ScrewsAlloy 20 Pan Head Machine ScrewsAlloy 20 Phillips Pan Head ScrewsAlloy 20 Slotted Pan Head ScrewsAlloy 20 Hex Drive Pan Head ScrewsUNS N08020 Pan Head Screws2.4660 Pan Head Screws20Cb-3 Pan Head ScrewsCarpenter 20 Pan Head ScrewsIncoloy 20 Pan Head ScrewsASTM B473 Pan Head ScrewsNACE MR0175 Pan Head ScrewsDIN 7985 Alloy 20 ScrewsISO 7045 Alloy 20 ScrewsASME B18.6.3 Alloy 20 Screwssulfuric acid resistant screwscorrosion resistant machine screwschemical processing screwssour service screwspharmaceutical grade screwsfood processing screws

Complete Range of Alloy 20 Pan Head Screws – Configurations

Metric Pan Head Screws (DIN 7985 / ISO 7045)

Alloy 20 metric pan head screws manufactured to DIN 7985 and ISO 7045 standards. Features a rounded top head with a flat bearing surface, providing excellent drive engagement and aesthetic appearance. Available with Phillips, slotted, and hex drive configurations. Precision rolled threads for superior strength and corrosion resistance. Ideal for high-temperature corrosive applications up to 500°C. Available in sizes from M2 to M24 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 Pan Head Screws (ASME B18.6.3)

Alloy 20 inch pan head screws manufactured to ASME B18.6.3 standards. Features a rounded top head with a flat bearing surface, designed for American standard applications. Available with Phillips, slotted, and combination drive configurations. Precision rolled UNC and UNF threads for superior fatigue resistance. Available in sizes from #2 to 1" in various lengths. Supplied with passivated finish per ASTM A967. Ideal for oil & gas, marine, and industrial applications requiring NACE MR0175 compliance.

Custom & Specialty Pan Head Screws

Need a special drive configuration, unusual thread size, or custom head dimensions for your corrosive application? RAYCHIN engineers work with you to produce custom Alloy 20 pan head screws to your drawing. Options include Torx drive, tamper-resistant drive, extra-low head height, and custom head diameters. 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 Pan 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. Corrosion rates typically below 0.1-0.5 mm/year across all concentrations.

Versatile Head Design

The pan head profile provides a low-profile, rounded top with flat bearing surface, ideal for general-purpose fastening applications. Available with multiple drive options including Phillips, slotted, hex, and Torx for maximum versatility.

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.

Multiple Drive Options

Available with Phillips, slotted, hex, Torx, and combination drives to suit assembly requirements. Deep, accurate drive recesses ensure positive engagement and torque transfer without cam-out.

Temperature Versatility

Maintains useful mechanical properties up to 500°C (930°F), suitable for heat exchanger and process equipment applications at elevated temperatures.

Pan Head Screw Design & Standards

Dimensional Standards

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

MetricDIN 7985, ISO 7045, ISO 7046
InchASME B18.6.3, SAE J82
AerospaceNAS603, NAS604 (inch)
BritishBS 4183

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

Drive Options

  • Phillips Drive: PH0 through PH4 sizes for positive driver engagement.
  • Slotted Drive: Standard slotted for simple tooling.
  • Hex Drive: Internal hex socket for higher torque applications.
  • Torx Drive: T6 through T60 for maximum torque transfer and reduced cam-out.
  • Combination Drive: Phillips/slotted or Torx/slotted for tool flexibility.

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 Pan Head Screws

RAYCHIN LIMITED manufactures Alloy 20 pan head 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 Pan Head Screws

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 pan 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.

Country / RegionStandard / SpecificationDesignation / Grade
USAASTM B473 / ASME SB473, ASTM B462, ASTM F2281, UNS N08020Alloy 20 · 20Cb-3 · Carpenter 20 · Incoloy 20
Germany (DIN)W. Nr. 2.4660, DIN 17744, DIN 7985 (pan head screws)2.4660 · NiCr20CuMo
Europe (CEN)EN 10269 (for fasteners), EN 100951.4500 (similar designation)
France (NF)NF A35-572/573Z2NCDU25-20
UK (BS)BS 3076, BS 4183 (pan head screws)NA 20
China (GB)GB/T 15007, GB/T 1220, GB/T 818 (pan head screws)NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)JIS G4903, JIS G4904, JIS B1111 (machine screws)NCF 20
ISOISO 15156-3 (NACE MR0175), ISO 7045 (pan head screws)UNS N08020
NACENACE MR0175 / ISO 15156Alloy 20 (qualified for sour service)
APIAPI 20FAlloy 20

UNS N08020 2.4660 ASTM B473 ASME SB473 NACE MR0175 20Cb-3 Carpenter 20 Incoloy 20 DIN 7985 ISO 7045 ASME B18.6.3

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

Our Alloy 20 pan 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.

ElementASTM B473 / ASME SB473 (Range %)Typical (analysis)
Nickel (Ni)32.0 – 38.034.0
Chromium (Cr)19.0 – 21.020.0
Copper (Cu)3.0 – 4.03.5
Molybdenum (Mo)2.0 – 3.02.5
Niobium + Tantalum (Nb+Ta)8 x C min – 1.0 max0.5
Carbon (C)≤ 0.070.03
Manganese (Mn)≤ 2.001.2
Phosphorus (P)≤ 0.0450.020
Sulfur (S)≤ 0.0350.010
Silicon (Si)≤ 1.000.5
Iron (Fe)BalanceBalance

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 Pan Head Screws (per ASTM B473)

Alloy 20 pan 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)

Size RangeTensile Strength (min)Yield Strength 0.2% Offset (min)Elongation (min)Reduction of Area (min)
All sizes550 MPa (80 ksi)240 MPa (35 ksi)30%50%

Typical Mechanical Properties (Solution Annealed)

PropertyTypical ValueNotes
Ultimate Tensile Strength620 MPa (90 ksi)Exceeds minimum requirements
Yield Strength (0.2% Offset)300 MPa (45 ksi)Exceeds minimum requirements
Elongation40%Excellent ductility
Hardness (Brinell)217 HB maxTypically 150-190 HB
Hardness (Rockwell C)19 HRC maxTypically 10-15 HRC
Modulus of Elasticity193 GPa (28,000 ksi)At room temperature
Poisson's Ratio0.31—

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 500°C (930°F), suitable for heat exchanger and process equipment applications.

TemperatureYield Strength (typical)Tensile Strength (typical)Retention (%)
Room Temperature (20°C)300 MPa620 MPa100%
100°C (212°F)275 MPa590 MPa90-95%
200°C (392°F)260 MPa570 MPa85-90%
300°C (572°F)250 MPa550 MPa80-85%
400°C (752°F)240 MPa530 MPa75-80%
500°C (932°F)230 MPa500 MPa70-75%

Note: For service above 500°C, nickel-based alloys such as Inconel 625 or 718 are recommended.

Physical Properties

PropertyValue
Density8.08 g/cm³ (0.292 lb/in³)
Melting Point1357 – 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 Capacity0.45 J/g·°C
Electrical Resistivity135.9 × 10⁻⁶ ohm-cm
Magnetic Permeability≤ 1.02 (non-magnetic)

Exceptional Corrosion Resistance of Alloy 20 Pan 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 pan 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.

ConcentrationTemperatureCorrosion Rate
Up to 50% H₂SO₄Up to 80°C< 0.1 mm/year (excellent)
50-80% H₂SO₄Up to 50°C< 0.5 mm/year (good)
80-95% H₂SO₄Room temperature< 0.1 mm/year (excellent)
96%+ H₂SO₄Elevated< 0.5 mm/year (good)

Alloy 20 maintains low corrosion rates across the full sulfuric acid concentration range, particularly excelling in the critical 20-80% concentration at elevated temperatures.

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 pan 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.

Resistance to Other Media

EnvironmentResistance LevelNotes
Nitric AcidGoodChromium provides resistance to oxidizing acids
Hydrochloric AcidModerateLimited resistance at higher concentrations/temperatures
Hydrofluoric AcidGoodResistant to all concentrations at room temperature, up to 10% HF at 70°C
Mixed Acids (H₂SO₄ + HNO₃)ExcellentWidely used in nitration processes
Caustic SolutionsGoodResistant to caustic soda and potash
SeawaterGoodResistant to pitting and crevice corrosion
Sour Service (H₂S)ExcellentQualified per NACE MR0175/ISO 15156

Special focus: Alloy 20 Pan Head Screws for Corrosive Applications

For critical applications requiring exceptional corrosion resistance and versatile fastening, RAYCHIN offers Alloy 20 pan 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, agitator assemblies.
  • Phosphoric Acid Production: Reactor access covers, evaporator inspection ports, heat exchanger heads, mixer blade attachments, piping flanges.
  • Chemical Processing: Reactor manway covers, distillation column access ports, valve bonnet fasteners, agitator blade screws, instrument connections.
  • Oil & Gas / Sour Service: NACE MR0175 compliant pan head screws for instrument panels, valve covers, 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 7985 (metric), ISO 7045 (metric), ASME B18.6.3 (inch), NAS603/NAS604 (aerospace).
  • Drive Types: Phillips, slotted, hex, Torx, combination drives.
  • Thread Classes: 2A, 3A, UNJF-3A, 6g, 6H.
  • Sizes: M2 through M24, #2 through 1".
  • Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU.

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

Why RAYCHIN LIMITED – The Alloy 20 Pan 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 pan 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 pan head screws meet applicable ASTM B473, ASME SB473, NACE MR0175, and screw standards including DIN 7985, ISO 7045, ASME B18.6.3.

Precision head forming & drive forming

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

Custom solutions

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

Contact the Alloy 20 pan head screw experts today

Request a quote for Alloy 20 pan head screws, metric pan head screws, inch pan head machine screws, Phillips drive pan head screws, slotted pan 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.

sales@ray-chin.com | +86 534 2166 566

Our team speaks English, German, Mandarin, and Japanese – ready for your global procurement.


RAYCHIN LIMITED — World-class manufacturer of Alloy 20 pan head screws (metric pan head screws · inch pan head machine screws · Phillips pan head screws · slotted pan head screws · hex drive pan head screws) for chemical processing, sulfuric acid plants, phosphoric acid production, oil & gas, pharmaceutical, and food processing industries. Specialists in nickel-iron-chromium superalloy fasteners for corrosive applications requiring versatile, corrosion-resistant screws up to 500°C. Manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN, KS standards. UNS N08020 · 2.4660 · 20Cb-3 · Carpenter 20 · Incoloy 20 · ASTM B473 · ASME SB473 · NACE MR0175 · API 20F · DIN 7985 · ISO 7045 · ASME B18.6.3 · NAS603 · NAS604 · NS1403 · NCF 20 compliant.

Head office: Taoyuan Road, East District, Pingyuan Economic Development Zone, Shandong Province, China

Alloy 20 pan head screws USA, Alloy 20 machine screws Europe, Alloy 20 Phillips pan head screws Germany, UNS N08020 pan head screws Japan, 2.4660 pan head screws UK, Carpenter 20 pan head screws Asia, NACE MR0175 pan head screws Middle East, sulfuric acid resistant screws, corrosion resistant machine screws, chemical processing screws, sour service screws, pharmaceutical grade screws, food processing screws, DIN 7985 screws, ISO 7045 screws, ASME B18.6.3 screws.



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