Alloy 20 Lock Nuts
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 Lock Nuts · All-Metal · Nylon Insert · Heavy Hex · Jam · CustomAlloy 20 Lock Nuts: Nickel-Iron-Chromium Superalloy Self-Locking Nuts for Extreme Corrosive & Vibration-Prone Environments
RAYCHIN LIMITED is a recognized expert in Alloy 20 lock nuts — from Alloy 20 all-metal lock nuts, Alloy 20 nylon insert lock nuts, Alloy 20 heavy hex lock nuts, Alloy 20 jam lock nuts to custom non-standard lock nut 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 lock nut applications in sulfuric acid service, phosphoric acid handling, heat exchangers, pressure vessels, chemical processing, oil & gas (sour service), pharmaceuticals, and food processing equipment requiring vibration-resistant fastening. Alloy 20 lock nuts are specifically designed to prevent loosening under vibration, thermal cycling, and dynamic loads while providing superior 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 lock nuts manufactured to NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN and KS standards. Engineered for extreme environments where corrosion resistance and vibration resistance are critical. Alloy 20 lock nuts are supplied in solution annealed condition with full traceability and third-party certifications.
Complete Range of Alloy 20 Lock Nuts – Types & Configurations
Alloy 20 All-Metal Lock Nuts
Alloy 20 all-metal lock nuts manufactured to DIN 980, ISO 7042, and ASME B18.16.6 standards. Features an integral locking mechanism through controlled thread deformation or elliptical offset, providing prevailing torque without any non-metallic inserts. Ideal for high-temperature applications up to 600°C where nylon inserts cannot be used. The all-metal design ensures consistent locking torque even after repeated use. Available in hex and heavy hex configurations. Sizes from 1/4" to 4" (M6 to M100). Supplied in solution annealed condition per ASTM B473. Suitable for heat exchangers, pressure vessels, and high-temperature chemical processing equipment.
Alloy 20 Nylon Insert Lock Nuts
Alloy 20 nylon insert lock nuts manufactured to DIN 985, DIN 982, ISO 7040, ISO 10511, and IFI 100/107 standards. Features a non-metallic locking element (nylon ring) that deforms elastically when engaged with the mating thread, providing consistent prevailing torque without damaging the bolt threads. Ideal for applications requiring repeated assembly and disassembly up to 120°C. The nylon insert also seals against leakage along the thread path. Available in hex and heavy hex configurations. Sizes from 1/4" to 2" (M6 to M48). Suitable for pharmaceutical, food processing, and instrument applications where vibration resistance and corrosion protection are essential.
Alloy 20 Heavy Hex Lock Nuts
Alloy 20 heavy hex lock nuts manufactured to ASME B18.2.2, DIN 6915, and ASTM A563 specifications with locking features. Features a larger wrenching surface for increased bearing area, combined with all-metal or nylon insert locking elements. Essential for high-pressure flange connections, pressure vessel closures, and heavy equipment subject to vibration. Available in both all-metal (to 600°C) and nylon insert (to 120°C) versions. Sizes from 1/2" to 4" (M12 to M100). NACE MR0175 compliant for sour service applications. Supplied with matching Alloy 20 stud bolts for complete bolting sets.
Alloy 20 Jam Lock Nuts
Alloy 20 jam lock nuts manufactured to DIN 439, ISO 4035, and ASME B18.2.2 standards with locking features. Reduced height nuts designed for limited clearance applications, available with all-metal or nylon insert locking elements. Ideal for valve assemblies, instrumentation, and control systems where space is constrained but vibration resistance is required. Available in hex and heavy hex configurations. Sizes from 1/4" to 2" (M6 to M48). Precision machined from solution annealed Alloy 20 for optimum corrosion resistance.
Alloy 20 Lock Nuts – API & NACE Compliant
Alloy 20 lock nuts certified to NACE MR0175 / ISO 15156 for sour service applications in oil and gas industry. Available in all-metal configuration with controlled hardness ≤ 35 HRC per API 20F BSL2 & BSL3 requirements. Suitable for wellhead equipment, valve assemblies, subsea connections, and refinery applications exposed to H₂S environments. Available in all configurations with 100% hardness testing and dimensional verification. API 6A closure lock nuts available with full traceability and material certifications per ASTM B473.
Custom & Specialty Alloy 20 Lock Nuts
Need a special locking configuration, unusual thread size, or custom performance requirements for your corrosive application? RAYCHIN engineers work with you to produce custom Alloy 20 lock nuts to your drawing. Options include slotted lock nuts, castle lock nuts, coupling lock nuts, and nuts with special locking elements. 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 Lock Nuts
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 lock nuts would fail.
Vibration Resistance
All-metal and nylon insert designs provide reliable prevailing torque to prevent loosening under vibration, thermal cycling, and dynamic loads. Meets IFI 100/107 and DIN torque requirements.
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.
Temperature Versatility
All-metal lock nuts serviceable up to 600°C; nylon insert lock nuts ideal for repeated use up to 120°C. Both maintain corrosion resistance across temperature range.
Lock Nut Design & Performance Characteristics
All-Metal Lock Nut Design
All-metal lock nuts achieve prevailing torque through controlled deformation of the threads, typically in the top portion of the nut. Common designs include:
- Elliptical Offset: The top threads are formed into an elliptical shape, creating interference with the mating bolt threads.
- Thread Deflection: Selected threads are precisely displaced to create frictional resistance.
- Slot & Collar: Slots cut into the nut with a compressed collar that exerts force on the bolt threads.
Advantages: Temperature capability to 600°C, reusable, no material compatibility concerns. Meets performance requirements of DIN 980 and IFI 100/107.
Nylon Insert Lock Nut Design
Nylon insert lock nuts feature a non-metallic locking ring (typically nylon 6/6) crimped into the nut's top. When engaged with the mating bolt, the nylon deforms elastically, creating prevailing torque through friction.
- Temperature Limit: Continuous service to 120°C (250°F).
- Reusability: 5-15 cycles typical depending on specification.
- Sealing: Nylon ring provides additional sealing against leakage along thread path.
Meets performance requirements of DIN 985, DIN 982, ISO 7040, and IFI 100/107 Grade B.
Prevailing Torque Requirements
Our Alloy 20 lock nuts meet or exceed the following prevailing torque specifications:
First removal torque typically 30-70% of installation torque depending on size and configuration.
Manufacturing Standards for Alloy 20 Lock Nuts
RAYCHIN LIMITED manufactures Alloy 20 lock nuts to the following national and international standards, ensuring full compliance for projects worldwide. Both standard and non-standard custom configurations are available.
Lock Nut Dimensional & Performance Standards
All dimensional standards available in UNC, UNF, and metric thread configurations. Standard sizes from 1/4" to 4" (M6 to M100). Proof load testing per ASTM A453 ensures compatibility with mating bolts.
International Standards & Global Designations for Alloy 20 Lock Nuts
To serve clients worldwide, RAYCHIN LIMITED manufactures Alloy 20 lock nuts 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 NS1403 NCF 20
Chemical Composition (Weight %) – Alloy 20 (UNS N08020 / 2.4660)
Our Alloy 20 lock nuts 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.
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 Lock Nuts (per ASTM B473)
Alloy 20 lock nuts 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. Proof load testing ensures compatibility with mating bolts.
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, suitable for heat exchanger and process equipment applications.
Note: For service above 600°C, nickel-based alloys such as Inconel 625 or 718 are recommended. Nylon insert lock nuts limited to 120°C maximum service temperature.
Physical Properties
Exceptional Corrosion Resistance of Alloy 20 Lock Nuts
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 lock nuts 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. All-metal lock nuts maintain full corrosion resistance up to 600°C; nylon insert versions to 120°C.
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. Both all-metal and nylon insert lock nuts perform well in phosphoric acid environments.
Chloride Stress Corrosion Cracking (SCC) Resistance
With 32-38% nickel content, Alloy 20 lock nuts 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. The locking mechanism does not compromise corrosion resistance.
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
Critical Corrosion Considerations for Lock Nuts
- Sulfuric Acid Applications: Alloy 20 is the preferred material for lock nuts in sulfuric acid environments up to moderately elevated temperatures. Copper content is critical for performance. All-metal lock nuts recommended for continuous service above 120°C.
- Phosphoric Acid Service: Excellent resistance in wet process phosphoric acid, even with fluoride impurities. Widely used in fertilizer plant lock nuts for vibratory equipment.
- Chloride Environments: Immunity to chloride SCC makes Alloy 20 ideal for marine and brackish water applications where vibration-resistant fastening is required.
- NACE MR0175 Compliance: Qualified for sour service (sulfide stress cracking resistance) in oilfield equipment per NACE MR0175/ISO 15156. All-metal lock nuts recommended for H₂S service.
- Temperature Limitations: All-metal lock nuts serviceable to 600°C. Nylon insert lock nuts limited to 120°C maximum continuous service. Above 120°C, nylon degrades and locking function is lost.
- 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.
Special focus: Alloy 20 Lock Nuts for Corrosive & Vibration-Prone Applications
For critical applications requiring both exceptional corrosion resistance and vibration-resistant fastening, RAYCHIN offers Alloy 20 lock nuts manufactured to ASTM, ASME, NACE, and customer-specific specifications. Our capabilities include:
- Sulfuric Acid Plants: Heat exchanger lock nuts, piping flange lock nuts, pump lock nuts, acid cooler fasteners, pickling equipment, agitator assemblies subject to vibration.
- Phosphoric Acid Production: Reactor lock nuts, evaporator lock nuts, heat exchanger lock nuts, piping systems, mixer blade lock nuts.
- Chemical Processing: Reactor closure lock nuts, distillation column lock nuts, piping systems, valve assembly lock nuts, agitator lock nuts, pump lock nuts.
- Oil & Gas / Sour Service: NACE MR0175 compliant all-metal lock nuts for wellhead equipment, valve assemblies, subsea connections, refinery piping subject to vibration.
- Pharmaceutical Manufacturing: Reactor lock nuts, clean room equipment, process piping, sanitary fittings, instrument connections (nylon insert for frequent assembly).
- Food Processing: Mixer lock nuts, tank lock nuts, process equipment, sanitary piping systems, heat exchanger lock nuts.
- Marine Applications: Seawater piping lock nuts, pump lock nuts, valve assembly lock nuts, offshore platform equipment subject to wave-induced vibration.
- Pulp & Paper Industry: Digester lock nuts, bleach plant lock nuts, paper machine lock nuts, chemical recovery equipment.
- Product Types: All-metal lock nuts (DIN 980, ISO 7042), nylon insert lock nuts (DIN 985, ISO 7040), heavy hex lock nuts (DIN 6915 with locking), jam lock nuts (DIN 439 with locking).
- Thread Classes: 2B, 3B, UNJ-3B per AS8879 for aerospace applications.
- 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 lock nuts 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 Alloy 20 bolts and studs for complete locking fastener assemblies. Material certifications included.
Why RAYCHIN LIMITED – The Alloy 20 Lock Nut Authority
Metallurgical competence
Engineers on staff with deep expertise in nickel-based superalloys and locking fastener technology. We ensure proper solution annealing (1030-1120°C) for optimal corrosion resistance across all Alloy 20 lock nuts. Every heat is verified by in-house PMI testing to confirm chemistry. With 32-38% nickel and copper-molybdenum additions, our lock nuts provide exceptional resistance to sulfuric acid, phosphoric acid, and chloride stress corrosion cracking while maintaining reliable prevailing torque.
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 lock nuts meet applicable ASTM B473, ASME SB473, NACE MR0175, and lock nut standards including DIN 980, DIN 985, IFI 100/107.
Precision forming & locking element integration
In-house CNC tapping, thread forming, and precision locking element integration ensure consistent thread geometry and reliable prevailing torque. All-metal lock nuts feature precisely controlled thread deformation; nylon insert lock nuts feature securely crimped locking elements. 100% torque testing available. Ultrasonic cleaning and passivation available for critical pharmaceutical and food processing applications.
Custom solutions
Need a special locking configuration, unusual thread size, or custom performance requirements for your corrosive application? Our engineering team works with you to produce custom Alloy 20 lock nuts to your drawing. We provide specialized surface treatments, passivation, and NACE MR0175 compliant processing per customer requirements.
Contact the Alloy 20 lock nut experts today
Request a quote for Alloy 20 lock nuts, all-metal lock nuts, nylon insert lock nuts, heavy hex lock nuts & custom configurations – any global standard (NAS, AN, MS, ANSI, ASTM, ASME, SAE, API, NACE, ISO, DIN, KS), any quantity. Inquire about sulfuric acid resistant lock nuts, NACE MR0175 sour service requirements, or high-temperature locking applications.
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