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Alloy 20 nuts are engineered fasteners designed for highly corrosive environments where conventional stainless steel fails, particularly in chemical processing and acid-handling systems. Manufactured from a nickel-iron-chromium alloy with molybdenum and copper additions, these nuts offer exceptional resistance to sulfuric acid, chloride stress corrosion cracking, and pitting corrosion. Typically produced in compliance with ASTM B462, ASTM B473, and DIN/ISO standards, Alloy 20 nuts are widely used across chemical plants, pharmaceuticals, and marine installations.
These fasteners play a critical role in maintaining joint integrity under aggressive chemical exposure and elevated temperatures. Precision threading, dimensional accuracy, and material traceability are essential for performance in such demanding conditions. KK Fasteners supplies Alloy 20 nuts to global industries, ensuring consistent quality, compliance with international standards, and reliable delivery across critical applications.
| Parameter | Details |
|---|---|
| Material | Alloy 20 (UNS N08020) |
| Grades | ASTM B462, ASTM B473 |
| Size Range | M3 to M64 / 1/8" to 2" |
| Thread Type | Metric (ISO), UNC, UNF, BSW |
| Standards | DIN 934, ISO 4032, ASTM B18.2.2 |
| Types | Hex Nuts, Heavy Hex Nuts, Lock Nuts, Jam Nuts |
| Surface Finish | Plain, PTFE Coated, Passivated |
| Tensile Strength | ≥ 620 MPa |
| Hardness | ≤ 95 HRB |
| Temperature Resistance | Up to 540°C (oxidizing environments) |
| Alloy 20 | Ni | C | Mo | Mn | Si | Fe | Cu | S | P | Cr |
| 32 – 38 | 0.02 max | 2 – 3 | 1 – 2 | 0.7 max | Bal | 3 – 4 | 0.005 max | 0.02 max | 19 – 21 |
| Density | Melting Point | Yield Strength (0.2%Offset) | Tensile Strength | Elongation |
| 8.1 g/cm3 | 1443 °C (2430 °F) | Psi – 35000 , MPa – 241 | Psi – 80000 , MPa – 551 | 30 % |
| STANDARD | UNS | WERKSTOFF NR. | AFNOR | EN | JIS | BS | GOST |
| Alloy 20 | N08020 | 2.4660 | Z2NCUD31-20AZ | NiCr20CuMo | – | – | – |
All measurements in millimeters
Nominal Size or Basic Major Thread Diameter |
F |
G |
H |
||||||
Width Across Flats |
Width Across Corners |
Thickness |
|||||||
Basic |
Max |
Min |
Max |
Min |
Basic |
Max |
Min |
||
1/4 |
.2500 |
1/2 |
.500 |
.488 |
.577 |
.556 |
15/64 |
.250 |
.218 |
5/16 |
.3125 |
9/16 |
.562 |
.546 |
.650 |
.622 |
19/64 |
.314 |
.280 |
3/8 |
.3750 |
11/16 |
.688 |
.669 |
.794 |
.763 |
23/64 |
.377 |
.341 |
7/16 |
.4375 |
3/4 |
.750 |
.728 |
.866 |
.830 |
27/64 |
.441 |
.403 |
1/2 |
.5000 |
7/8 |
.875 |
.850 |
1.010 |
.969 |
31/64 |
.504 |
.464 |
9/16 |
.5625 |
15/16 |
.938 |
.909 |
1.083 |
1.037 |
35/64 |
.568 |
.526 |
5/8 |
.6250 |
1-1/16 |
1.062 |
1.031 |
1.227 |
1.175 |
39/64 |
.631 |
.587 |
3/4 |
.7500 |
1-1/4 |
1.250 |
1.212 |
1.443 |
1.382 |
47/64 |
.758 |
.710 |
7/8 |
.8750 |
1-7/16 |
1.438 |
1.394 |
1.660 |
1.589 |
55/64 |
.885 |
.833 |
1 |
1.0000 |
1-5/8 |
1.325 |
1.575 |
1.876 |
1.796 |
63/64 |
1.012 |
.956 |
1-1/8 |
1.1250 |
1-13/16 |
1.812 |
1.756 |
2.093 |
2.002 |
1-7/64 |
1.139 |
1.079 |
1-1/4 |
1.2500 |
2 |
2.000 |
1.938 |
2.309 |
2.209 |
1-7/32 |
1.251 |
1.187 |
1-3/8 |
1.3750 |
2-3/16 |
2.188 |
2.119 |
2.526 |
2.416 |
1-11/32 |
1.378 |
1.460 |
1-1/2 |
1.5000 |
2-3/8 |
2.375 |
2.300 |
2.742 |
2.622 |
1-15/32 |
1.505 |
1.433 |
1-5/8 |
1.6250 |
2-9/16 |
2.562 |
2.481 |
2.959 |
2.828 |
1-19/32 |
1.632 |
1.556 |
1-3/4 |
1.7500 |
2-3/4 |
2.750 |
2.662 |
3.175 |
3.035 |
1-23/32 |
1.759 |
1.679 |
2 |
2.0000 |
3-1/8 |
3.125 |
3.025 |
3.608 |
3.449 |
1-31/32 |
2.013 |
1.925 |
2-1/4 |
2.2500 |
3-1/2 |
3.500 |
3.388 |
4.041 |
3.862 |
2-13/64 |
2.251 |
2.155 |
2-1/2 |
2.5000 |
3-7/8 |
3.875 |
3.750 |
4.474 |
4.275 |
2-29/64 |
2.505 |
2.401 |
2-3/4 |
2.7500 |
4-1/4 |
4.250 |
4.112 |
4.907 |
4.688 |
2-45/64 |
2.759 |
2.647 |
3 |
3.0000 |
4-5/8 |
4.625 |
4.475 |
5.340 |
5.102 |
2-61/64 |
3.013 |
2.893 |
3-1/4 |
3.2500 |
5 |
5.000 |
4.838 |
5.774 |
5.515 |
3-3/16 |
3.252 |
3.124 |
3-1/2 |
3.5000 |
5-3/8 |
5.375 |
5.200 |
6.207 |
5.928 |
3-7/16 |
3.506 |
3.370 |
3-3/4 |
3.7500 |
5-3/4 |
5.750 |
5.562 |
6.640 |
6.341 |
3-11/16 |
3.670 |
3.616 |
4 |
4.0000 |
6-1/8 |
6.125 |
5.925 |
7.073 |
6.755 |
3-15/16 |
4.014 |
3.862 |
Where are Alloy 20 nuts used?
Alloy 20 nuts are used in industries where resistance to acidic corrosion and chemical attack is critical for maintaining joint integrity and operational safety.
Alloy 20 nuts are typically produced through hot forging or CNC machining, followed by threading operations that comply with ISO and ASTM tolerances. Each batch undergoes rigorous quality checks, including dimensional inspection using calibrated gauges, hardness testing, and surface finish verification to ensure corrosion resistance.
Material traceability is maintained through heat numbers and mill test certificates. At KK Fasteners, inspection protocols align with ISO 9001 standards, ensuring every shipment meets international compliance requirements. Additional testing such as PMI (Positive Material Identification) and corrosion testing can be conducted upon request for critical applications.
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Alloy 20 nuts are corrosion-resistant fasteners made from a nickel-iron-chromium alloy (UNS N08020). They are specifically designed for use in aggressive chemical environments, offering strong resistance to sulfuric acid, pitting, and stress corrosion cracking in critical industrial applications.
Yes, Alloy 20 nuts are highly resistant to sulfuric acid, particularly in concentrations up to around 70%. The alloy’s copper and molybdenum content improves its ability to withstand acidic corrosion, making it a preferred choice over stainless steel in chemical processing systems.
Alloy 20 nuts are manufactured according to ASTM standards such as ASTM B462 and ASTM B473, along with dimensional standards like DIN 934 and ISO 4032. These ensure proper mechanical strength, chemical composition, and dimensional accuracy for industrial use.
Selection depends on operating conditions such as chemical exposure, temperature, load requirements, and compatibility with mating fasteners. For highly corrosive or acidic environments, Alloy 20 nuts with PTFE coating or matched Alloy 20 bolts are typically recommended.
A reliable supplier should offer ISO-certified production, full material traceability, and compliance with ASTM and DIN standards. KK Fasteners supplies Alloy 20 nuts globally with documented quality checks, making it easier for procurement teams to ensure consistency and compliance.
Alloy 20 nuts are a critical solution for industries operating in aggressive chemical environments where reliability cannot be compromised. With strict quality control, global supply capability, and full material traceability, KK Fasteners supports industrial buyers with dependable fastening solutions. Request a quote or connect with the engineering team to discuss your exact specification requirements.
