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Alloy 20 Fasteners

Alloy 20 fasteners, 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) fasteners 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 fasteners 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

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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 Fasteners
SKU: 0

Specialist in Alloy 20 Fasteners · Bolts · Nuts · Screws · Washers · Stud Bolts · Threaded Rods · Custom

Alloy 20 Fasteners: Nickel-Iron-Chromium Superalloy Bolts, Nuts, Screws, Washers, Stud Bolts & Threaded Rods

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

RAYCHIN LIMITED is a recognized expert in Alloy 20 fasteners — from Alloy 20 bolts, Alloy 20 nuts, Alloy 20 screws, Alloy 20 washers, Alloy 20 stud bolts, Alloy 20 threaded rods to custom non-standard fastener 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 600°C (1112°F), making it the preferred material for fastener applications in sulfuric acid service, phosphoric acid handling, heat exchangers, pressure vessels, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment. Alloy 20 fasteners are specifically designed for applications requiring resistance to general corrosion, pitting, crevice corrosion, and stress corrosion cracking in aggressive media. 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 fasteners manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS standards. Engineered for extreme environments where corrosion resistance and reliability are critical. Alloy 20 fasteners are supplied in solution annealed condition with full traceability and third-party certifications.

Alloy 20 fastenersAlloy 20 boltsAlloy 20 nutsAlloy 20 screwsAlloy 20 washersAlloy 20 stud boltsAlloy 20 threaded rodsUNS N08020 fasteners2.4660 fasteners20Cb-3 fastenersCarpenter 20 fastenersIncoloy 20 fastenersASTM B473 boltsASME SB473 nutsNACE MR0175 fastenerssulfuric acid resistant fastenersphosphoric acid fastenerscorrosion resistant fastenerschemical processing fastenerssour service fastenershex head bolts Alloy 20heavy hex nuts Alloy 20socket head screws Alloy 20flat washers Alloy 20double end studs Alloy 20continuous thread rods

Complete Range of Alloy 20 Fasteners – Types & Configurations

Alloy 20 Bolts

Alloy 20 bolts manufactured to ASTM B473, ASME SB473, DIN 931/933, ISO 4014/4017, and ASME B18.2.1 standards. Available in hex head bolts, heavy hex bolts, flange bolts, carriage bolts, and eye bolts. Precision rolled threads for superior strength and corrosion resistance. Ideal for high-temperature applications up to 600°C in pressure vessels, flange connections, and structural assemblies exposed to aggressive chemicals. Available in sizes from 1/4" to 4" (M6 to M100) in various lengths. Supplied in solution annealed condition. Custom head styles available per drawing.

Alloy 20 Nuts

Alloy 20 nuts manufactured to ASTM B473, ASME SB473, DIN 934, ISO 4032, and ASME B18.2.2 standards. Available in hex nuts, heavy hex nuts, jam nuts, lock nuts, and slotted nuts. Precision tapped to Class 2B and 3B tolerances for reliable engagement with mating bolts and studs. Essential for corrosive service applications in chemical processing, pharmaceutical equipment, and food processing. Available in sizes from 1/4" to 4" (M6 to M100). Proof load testing ensures compatibility with mating fasteners. NACE MR0175 compliant for sour service applications.

Alloy 20 Screws

Alloy 20 screws manufactured to DIN 912, DIN 933, DIN 7380, ISO 4762, ISO 7380, and ASME B18.3 standards. Available in socket head cap screws, hex head screws, Torx drive screws, button head screws, flat head screws, and set screws. The alloy's excellent corrosion resistance makes these screws ideal for pharmaceutical reactors, food processing equipment, and chemical instrumentation. Available with various drive types and point styles. Precision rolled threads for superior fatigue resistance.

Alloy 20 Washers

Alloy 20 washers manufactured to ASME B18.22.1, DIN 125, DIN 9021, ISO 7089, and ASTM F436 standards. Available in flat washers, heavy washers, spring washers, and Belleville washers. Precision stamped or machined from solution annealed Alloy 20, these washers provide uniform load distribution under bolt heads and nuts. Ideal for heat exchanger flanges, vessel connections, and pump assemblies. Available in sizes from #0 to 4" (M1.6 to M100) with various thickness options. Passivated finish per ASTM A967.

Alloy 20 Stud Bolts

Alloy 20 stud bolts manufactured to ASME B16.5, DIN 938, ISO 4014, and API 6A standards. Available in double-end studs, fully threaded studs, and tap-end studs. Designed for flange connections, pressure vessel closures, and heat exchanger applications. The alloy's exceptional resistance to sulfuric and phosphoric acids makes these studs ideal for chemical plant piping systems. Available with or without reduced shank. Supplied with matching Alloy 20 nuts. NACE MR0175 compliant for sour service applications. Sizes from 1/4" to 4" (M6 to M100) with lengths up to 6 meters.

Alloy 20 Threaded Rods

Alloy 20 threaded rods manufactured to ASME B18.31.1M, DIN 975, and ISO 4014 standards. Continuous threads along the entire length allow for cutting to any required length for custom applications. Ideal for high-temperature corrosive environments requiring custom length fasteners, tension applications, and through-bolting. Available in diameters from 1/4" to 4" (M6 to M100) in lengths up to 6 meters. Precision rolled threads for superior strength and consistency. Used extensively in chemical processing, pharmaceutical manufacturing, and acid handling systems.

Key Benefits of Alloy 20 Fasteners

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.

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.

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.

Excellent Pitting Resistance

Molybdenum addition (2-3%) provides enhanced resistance to pitting and crevice corrosion in chloride-containing media, including seawater and brine solutions.

Good High-Temperature Performance

Maintains useful mechanical properties up to 600°C (1112°F), suitable for heat exchanger and process equipment applications at elevated temperatures.

Phosphoric Acid Resistance

Excellent resistance to phosphoric acid and mixed acid environments, making it the material of choice for fertilizer industry applications.

Manufacturing Standards for Alloy 20 Fasteners

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

NASANMSANSIASTMASMESAEAPINACEISODINKSJISGB

Alloy 20 Fastener Styles

Alloy 20 Screws	12 Point Screws Button Head Cap Screws Flat Head Screws Hex Head Cap Screws Pan Head Screws Security Screws Set Screws Socket Head Cap Screws Vented Screws	• DIN 603 / ISO 8677 • DIN 912 / ISO 4762 • DIN 913 / ISO 4026 • DIN 914 / ISO 4027 • DIN 915 / ISO 4028 • DIN 916 / ISO 4029 • DIN 921 • DIN 931 / ISO 4014 • DIN 933 / ISO 4017 • DIN 961 / ISO 8676 • DIN 965 / ISO 7046 • DIN 966 / ISO 7047 • DIN 7991 / ISO 10642 • DIN 7380 / ISO 7380 • DIN 84 / ISO 1207 • DIN 85 / ISO 1580 • DIN 34822 • DIN 34821 • DIN 7504 / ISO 15480 • DIN 7984 • DIN 963 / ISO 2009




















Alloy 20 Bolts	Hex Head Bolts Shoulder Bolts Wedge Anchor Bolts	• DIN 931 • DIN 933 • ISO 4014 • ISO 4017 • ISO 7370




Alloy 20 Nuts	Hex Nuts Lock Nuts	• DIN 439 / ISO 4035 • DIN 934 / ISO 4032 • DIN 985 / ISO 7040 • DIN 986 • DIN 980 / ISO 7042 / ISO 19513 • DIN 6923 / ISO 4161





Alloy 20 Studs/Rod	Studs Threaded Rod Weld Studs	• DIN 975 • DIN 976


Alloy 20 Washers	Flat Washers Lock Washer	• DIN 125 / ISO 7089 / ISO 7090 • DIN 126 / ISO 7091 • DIN 127 / ISO 7090 • DIN 9021 / ISO 7093



Alloy 20 Hose Clamps	Medium Duty Hose Clamps	--

Alloy 20 Screws

12 Point Screws	Alloy 20 12 point screws allow for higher torque to be applied than a socket head cap screw or head head bolt, however they are be less economical due to the complex head design. Available in 1/4" or larger sizes.	• IFI-115 • MIL SPEC • DIN 34822 • DIN 34821



Button Head Cap Screws	Alloy 20 button head screws offer a wide clamping area and low profile. They are best for fastening material that is too thin to counter bore.	• ASME B18.3 • ASME 18.3.4M • DIN 7380 / ISO 7380


Flat Head Screws	Alloy 20 flat head screws are most commonly offered in an 82° countersink angle, but can be customized to other angles from 60° -120° and are designed to be flush with the surface. Available in slotted and socket drivers. Phillips, 6-lobe, torx and tamperproof drivers in Inconel flat head screws can be made require special manufacturing.	• ASME B18.3 • ASME B18.3.6 • DIN 963 / ISO 2009 • DIN 965 / ISO 7046 • DIN 7991 / ISO 10642




Hex Head Cap Screws	Alloy 20 hex head cap screws offer the added washer face to the bolt head which is lacking on a hex bolt and tighter dimensional tolerances. Ideal for a high clamping force applications with ease of access. Generally availabe in #2 - 1/2" sizes and metric sizes.	• ASME B18.6.3 • DIN 931 / ISO 4014 • DIN 933 / ISO 4017 • DIN 961 / ISO 8676



Pan Head Screws	Alloy 20 pan head screws offer a rounded top are best used for small diameter faster needs. Offered in slotted and they are ideal for low torque applications.	• ASME B18.6.3 • DIN 7985 • DIN 921 • DIN 85 / ISO 1580 • DIN 84 / ISO 1207 (cheese head) • DIN 966 / ISO 7047 (raised counter sunk)







Security Screws	Unique driver designs offer these Alloy 20 screws resistance to unwanted tampering or removal due to the fact that they cannot be removed using an ordinary driver. Inconel security screws are available in several different drive styles, as well as custom per print.	--

Set Screws	Alloy 20 set screws are available in cup, cone, flat, dog and half-dog points. Set screws have no head and are equiped with a socket or slotted driver at one end.	• ASME B18.3 • DIN 913 / ISO 4026 • DIN 914 / ISO 4027 • DIN 915 / ISO 4028 • DIN 916 / ISO 4029




Socket Head Cap Screws	Alloy 20 socket head cap screws are ideal for limited access situations where there is little clearance around the screws. They offer a safe, reliable and economic solution.	• ASMET B18.3 • DIN 912 / ISO 4762 • DIN 7984


Vented Screws	Alloy 20 vented screws are best for vacuum environments because the hole drilled through its axis (from head through threads) allow gases and other contaminents to vent. Inconel vented screws are available in any style.	--

Alloy 20 Bolts

Hex Head Bolts	Alloy 20 hex bolts are similar to hex head cap screws but without the added washer face. They are ideal for high clamping force applications with ease access.	• ASME B18.2.1 • DIN 931 / ISO 4014 • DIN 933 / ISO 4017


Shoulder Bolts	Alloy 20 shoulder bolts are made up of a head, shoulder and threaded segment. The smooth shoulder section allows for rotating parts. Typically available with socket drivers.	• ASME • DIN 7379 / ISO 7379 • ISO 7370


Wedge Anchor Bolts	Alloy 20 wedge anchor bolts offer a safe secure fastening solution for attaching equipment and other materials to concrete in corrosive environments.	--

Alloy 20 Nuts

Hex Nuts	Alloy 20 hex nuts are available in a variety of styles including finished hex nuts, jam nuts and heavy hex nuts.	• ASME B18.16.3 • ASME B18.2.2 • DIN 439 / ISO 4035 • DIN 934 / ISO 4032 • DIN 986




Lock Nuts	Alloy 20 lock nuts are available in all metal and polymer insert styles. All-metal lock provide even load distribution and can be used at high temperatures. Polymer insert styles are more economical and are best for temperatures under than 350°F.	• ASME B18.16.3M • DIN 980 / ISO 7042 / ISO 19513 • DIN 6923 / ISO 4161 • DIN 985 / ISO 10511 / ISO 7040

Alloy 20 Studs & Threaded Rod

Studs	Alloy 20 studs are fully threaded or partially threaded and made to custom lengths.	• ASME B18.31.2 • DIN 976

Threaded Rod	Alloy 20 threaded rod or all thread are available in lengths greater than 1 foot. Minimum order quantity is a total of 6 feet of length.	• ASME B1.1 • DIN 975

Weld Studs	Alloy 20 weld studs are available in both arc or capacitor discharge (CD) styles. Weld studs provide an extremely secure fastening solution when one side of the stud needs to be permanently fix to a part and the other side with the threads accessible.	--

Alloy 20 Washers

Flat Washers	Alloy 20 washers are most commonly offered in SAE sizes, but also availabe in USS, oversized and custom sizes upon request.	• ASME 18.21.1 • SAE / USS • DIN 125 / ISO 7089 / ISO 7090 • DIN 126 / ISO 7091




Lock Washers	Alloy 20 lock washers are offered as split lock washers. Belleville spring lock washers can also be made upon request.	• ASME B18.21.1 • DIN 127 / ISO 7090 • DIN 6796 / ISO 10690

Fastener Dimensional Standards

Type	DIN	ISO	ASME	ASTM / API
Hex Bolts (Partial Thread)	DIN 931	ISO 4014	ASME B18.2.1	ASTM B473
Hex Bolts (Full Thread)	DIN 933	ISO 4017	ASME B18.2.1	ASTM B473
Heavy Hex Bolts	DIN 6914	ISO 7412	ASME B18.2.1	ASTM B473
Hex Nuts	DIN 934	ISO 4032	ASME B18.2.2	ASTM B473
Heavy Hex Nuts	DIN 6915	ISO 4034	ASME B18.2.2	ASTM B473
Socket Head Cap Screws	DIN 912	ISO 4762	ASME B18.3	ASTM B473
Flat Washers	DIN 125	ISO 7089	ASME B18.22.1	ASTM F436
Double-End Studs	DIN 938		ASME B16.5	ASTM B473 / API 6A
Threaded Rods	DIN 975		ASME B18.31.1M	ASTM B473

All dimensional standards available in UNC, UNF, and metric thread configurations. Standard sizes from 1/4" to 4" (M6 to M100). Custom sizes available upon request.

International Standards & Global Designations for Alloy 20 Fasteners

To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 fasteners 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	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	NS1403 · 0Cr20Ni35Mo3Cu4Nb
Japan (JIS)	JIS G4903, JIS G4904	NCF 20
ISO	ISO 15156-3 (NACE MR0175)	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 NS1403 NCF 20

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

Our Alloy 20 fasteners 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 after welding.

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 in the as-welded condition.

Complete Mechanical Properties of Alloy 20 Fasteners (per ASTM B473)

Alloy 20 fasteners are supplied in the solution annealed condition (typically 1030-1120°C followed by rapid quenching). The data below represent minimum requirements per ASTM B473 / ASME SB473 unless otherwise noted. Proof load testing ensures compatibility with mating nuts.

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 (45 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	195 GPa (28,300 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, 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%
200°C (392°F)	240 MPa	550 MPa	80-85%
300°C (572°F)	220 MPa	520 MPa	75-80%
400°C (752°F)	210 MPa	500 MPa	70-75%
500°C (932°F)	200 MPa	480 MPa	65-70%
600°C (1112°F)	180 MPa	450 MPa	60-65%

Note: Alloy 20 is not typically used for high-strength applications above 600°C. For service above 600°C, nickel-based alloys such as Inconel 625 or 718 are recommended.

Physical Properties

Property	Value
Density	8.05 g/cm³ (0.291 lb/in³)
Melting Point	1370 – 1430°C (2500 – 2600°F)
Thermal Expansion Coefficient (20-100°C)	16.2 x 10⁻⁶ /°C
Thermal Conductivity (20°C)	12.5 W/m·K
Specific Heat Capacity	0.45 J/g·°C
Electrical Resistivity	10.8 × 10⁻⁵ ohm-cm
Magnetic Permeability	≤ 1.02 (non-magnetic)

Exceptional Corrosion Resistance of Alloy 20 Fasteners

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 fasteners 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.

Concentration	Temperature	Corrosion Rate
Up to 50% H₂SO₄	Up to 80°C	< 0.1 mm/year (excellent)
50-80% H₂SO₄	Up to 50°C	< 0.13 mm/year (good)
80-95% H₂SO₄	Room temperature	< 0.1 mm/year (excellent)

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 fasteners 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 calculated as:

PRE = Cr + 3.3Mo + 30N (nitrogen content low in Alloy 20)

Alloy 20 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	Resistant to pitting and crevice corrosion in static seawater
Sour Service (H₂S)	Excellent	Qualified per NACE MR0175/ISO 15156

Critical Corrosion Considerations for Fasteners

Sulfuric Acid Applications: Alloy 20 is the preferred material for fasteners in sulfuric acid environments up to moderately elevated temperatures. Copper content is critical for performance.
Phosphoric Acid Service: Excellent resistance in wet process phosphoric acid, even with fluoride impurities. Widely used in fertilizer plant fasteners.
Chloride Environments: Immunity to chloride SCC makes Alloy 20 ideal for marine and brackish water applications where 304/316 stainless steels may fail.
NACE MR0175 Compliance: Qualified for sour service (sulfide stress cracking resistance) in oilfield equipment per NACE MR0175/ISO 15156.
Temperature Limitations: Maximum service temperature for continuous service is 600°C (1112°F). Above this temperature, strength decreases and oxidation may become significant.
Galvanic Corrosion: When paired with carbon steel or less noble materials, galvanic corrosion should be considered. Alloy 20 is cathodic to most steels.
Non-Magnetic Property: Alloy 20 is essentially non-magnetic (permeability ≤ 1.02), suitable for applications requiring non-magnetic components.
Weldability: Niobium stabilization prevents intergranular corrosion in the heat-affected zone, allowing welding without post-weld heat treatment.

Heat Treatment & Microstructural Stability of Alloy 20 Fasteners

Optimal corrosion resistance in Alloy 20 fasteners is achieved through solution annealing:

Solution Annealing: Heat to 1030-1120°C (1885-2050°F) followed by rapid quenching (water or air). This dissolves any precipitated carbides and ensures homogeneous distribution of alloying elements for maximum corrosion resistance.
Stabilization: Niobium (columbium) addition (8 x C min) ties up carbon as stable NbC carbides, preventing chromium carbide precipitation at grain boundaries during welding or slow cooling. This ensures resistance to intergranular corrosion in the as-welded condition.

All fasteners are supplied in the solution annealed condition to ensure optimum corrosion resistance. Cold worked fasteners are available for higher strength applications but may have slightly reduced corrosion resistance in severe environments.

Special focus: Alloy 20 Fasteners for Corrosive & Critical Applications

For critical applications requiring exceptional corrosion resistance, RAYCHIN offers Alloy 20 fasteners manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:

Sulfuric Acid Plants: Heat exchanger bolts, piping flanges, pump fasteners, acid coolers, pickling equipment, acid storage tanks.
Phosphoric Acid Production: Reactor bolts, evaporator fasteners, heat exchanger studs, piping systems, agitator assemblies.
Fertilizer Industry: Granulator fasteners, dryer bolts, conveyor systems, mixer blades and fasteners.
Chemical Processing: Reactor closure bolts, distillation column fasteners, piping systems, valve assembly bolts, thermowell fittings.
Pharmaceutical Manufacturing: Reactor fasteners, clean room equipment, process piping, sanitary fittings, instrument connections.
Food Processing: Mixer bolts, tank fasteners, process equipment, sanitary piping systems, heat exchanger studs.
Oil & Gas / Sour Service: NACE MR0175 compliant fasteners for wellhead equipment, valve assemblies, subsea connections, refinery piping.
Marine Applications: Seawater piping fasteners, pump bolts, valve assembly studs, offshore platform equipment.
Pollution Control: Flue gas desulfurization (FGD) system fasteners, scrubber bolts, ductwork studs.
Product Types: Hex bolts (ASME B18.2.1, DIN 931/933, ISO 4014/4017), heavy hex bolts, flange bolts, carriage bolts, eye bolts, U-bolts.
Nuts: Hex nuts (ASME B18.2.2, DIN 934, ISO 4032), heavy hex nuts (DIN 6915, ISO 4034), jam nuts (DIN 439, ISO 4035), lock nuts, slotted nuts.
Screws: Socket head cap screws (DIN 912, ISO 4762), hex head screws, Torx drive screws (DIN 7380, ISO 7380), button head, flat head, set screws.
Washers: Flat washers (ASME B18.22.1, DIN 125, ISO 7089), heavy washers, spring washers, Belleville washers.
Stud Bolts: Double-end studs (DIN 938, ASME B16.5), fully threaded studs (DIN 976), tap-end studs (DIN 835).
Threaded Rods: Fully threaded rods (DIN 975, ASME B18.31.1M) in lengths up to 6 meters.
Thread Classes: 2A, 3A, UNF, UNC, metric coarse/fine – all classes up to 3A/6g.
Surface Treatments: Passivation per ASTM A967, electropolishing for clean applications, PTFE coatings for anti-galling.
Certifications: EN 10204 3.1/3.2 material certifications, NACE MR0175, API 20F, PED 2014/68/EU, ASME compliance.

All Alloy 20 fasteners are supplied with full traceability and third-party NDT upon request. Available in all standard sizes from 1/4" to 4" (M6 to M100) with matching nuts for complete bolting sets. Material certifications included.

Why RAYCHIN LIMITED – The Alloy 20 Fastener 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 fasteners. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our fasteners 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 fasteners meet applicable ASTM B473, ASME SB473, and NACE MR0175 requirements.

Precision machining & threading

In-house CNC turning, cold heading, and precision thread rolling capabilities ensure consistent dimensional accuracy and thread geometry. Precision rolled threads provide superior fatigue life and corrosion resistance. 100% thread inspection available. Ultrasonic cleaning and passivation available for critical pharmaceutical and food processing applications.

Custom solutions

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

Contact the Alloy 20 fastener experts today

Request a quote for Alloy 20 bolts, nuts, screws, washers, stud bolts, threaded rods & custom configurations – any global standard (NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN, KS), any quantity. Inquire about sulfuric acid resistant fasteners, NACE MR0175 sour service requirements, or chemical processing applications.

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

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

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