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Alloy 20 washers are engineered fastening components designed for aggressive chemical environments where standard stainless steel grades fail under acid exposure. Manufactured from UNS N08020 nickel-iron-chromium alloy with controlled copper and molybdenum additions, these washers provide superior resistance to sulfuric acid, phosphoric acid, and chloride-induced corrosion. They are widely used in chemical processing plants, pharmaceutical equipment, marine systems, and heat exchanger assemblies where joint integrity and long-term stability are critical.
In high-stress bolted connections, Alloy 20 Washers distribute load evenly, reduce surface wear, and prevent galling between mating surfaces. Their dimensional precision ensures reliable torque retention in both static and dynamic assemblies. KK Fasteners supplies these washers with strict adherence to international standards, ensuring traceable material quality and consistent performance across global industrial applications.
| Parameter | Specification |
|---|---|
| Material | Alloy 20 (UNS N08020), Nickel-Iron-Chromium Alloy |
| Grades | Annealed, Cold Worked |
| Size Range | M3 to M100 / 1/8” to 4” |
| Standards | ASTM B473, ASTM B366, DIN 125, ISO 7089 |
| Thread Compatibility | Metric, UNC, UNF |
| Finish | Bright, Passivated, Polished, Anti-Galling Coated |
| Types | Flat Washers, Spring Washers, Lock Washers |
| Hardness | 150–220 HB (Annealed Condition) |
| 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 | – | – | – |
Bolt Size
|
USS
|
SAE
|
||||
OD (in.)
|
ID (in.)
|
Thickness
|
OD (in.)
|
ID (in.)
|
Thickness
|
|
1/8 (#6)
|
-
|
-
|
-
|
0.375
|
0.156
|
.036/.065
|
5/32 (#8)
|
-
|
-
|
-
|
0.438
|
0.188
|
.036/.065
|
3/16 (#10)
|
0.560
|
0.250
|
.036/.065
|
0.500
|
0.220
|
.036/.065
|
7/32 (#12)
|
-
|
-
|
-
|
0.562
|
0.250
|
.051/.080
|
1/4 (#14)
|
0.734
|
0.312
|
.051/.080
|
0.625
|
0.281
|
.051/.080
|
5/16
|
0.875
|
0.375
|
.064/.104
|
0.688
|
0.344
|
.051/.080
|
3/8
|
1.000
|
0.438
|
.064/.104
|
0.812
|
0.406
|
.051/.080
|
7/16
|
1.250
|
0.500
|
.064/.104
|
0.922
|
0.469
|
.051/.080
|
1/2
|
1.375
|
0.562
|
.086/.132
|
1.062
|
0.531
|
.074/.121
|
9/16
|
1.469
|
0.625
|
.086/.132
|
1.156
|
0.594
|
.074/.121
|
5/8
|
1.750
|
0.688
|
.108/.160
|
1.312
|
0.656
|
.074/.121
|
3/4
|
2.000
|
0.812
|
.122/.177
|
1.469
|
0.812
|
.108/.160
|
7/8
|
2.250
|
0.938
|
.136/.192
|
1.750
|
0.938
|
.108/.160
|
1
|
2.500
|
1.062
|
.136/.192
|
2.000
|
1.062
|
.108/.160
|
1 1/8
|
2.750
|
1.250
|
.136/.192
|
2.250
|
1.250
|
.108/.160
|
1 1/4
|
3.000
|
1.375
|
.136/.192
|
2.500
|
1.375
|
.136/.192
|
1 3/8
|
3.250
|
1.500
|
.153/.213
|
2.750
|
1.500
|
.136/.213
|
1 1/2
|
3.500
|
1.625
|
.153/.213
|
3.000
|
1.625
|
.153/.213
|
1 5/8
|
3.750
|
1.750
|
.153/.213
|
-
|
-
|
-
|
1 3/4
|
4.000
|
1.875
|
.153/.213
|
-
|
-
|
-
|
1 7/8
|
4.250
|
2.000
|
.153/.213
|
-
|
-
|
-
|
2
|
4.500
|
2.125
|
.153/.213
|
-
|
-
|
-
|
2 1/4
|
4.750
|
2.375
|
.320/.248
|
-
|
-
|
-
|
2 1/2
|
5.000
|
2.625
|
.210/.280
|
-
|
-
|
-
|
2 3/4
|
5.250
|
2.875
|
.228/.410S
|
-
|
-
|
-
|
3
|
5.500
|
3.125
|
.249/.327
|
-
|
-
|
-
|
Size |
USS |
SAE |
||||
|---|---|---|---|---|---|---|
Inside Diameter (A) |
Outside Diameter (B) |
Thickness (C) |
Inside Diameter (A) |
Outside Diameter (B) |
Thickness (C) |
|
#2 |
- |
- |
- |
3/32" |
1/4" |
0.020" |
#4 |
- |
- |
- |
1/8" |
5/16" |
0.032" |
#6 |
- |
- |
- |
5/32" |
3/8" |
0.049" |
#8 |
- |
- |
- |
3/16" |
7/16" |
0.049" |
#10 |
- |
- |
- |
7/32" |
1/2" |
0.049" |
#12 |
- |
- |
- |
1/4" |
9/16" |
0.065" |
1/4" |
5/16" |
0.734" |
0.065" |
9/32" |
5/8" |
0.065" |
5/16" |
3/8" |
7/8" |
0.083" |
11/32" |
11/16" |
0.065" |
3/8" |
7/16" |
1" |
0.083" |
13/32" |
13/16" |
0.065" |
7/16" |
1/2" |
1-1/4" |
0.083" |
15/32" |
15/16" |
0.065" |
1/2" |
9/16" |
1-3/8" |
0.109" |
17/32" |
1-1/16" |
0.095" |
9/16" |
5/8" |
1-15/32" |
0.109" |
19/32" |
1-5/32" |
0.095" |
5/8" |
11/16" |
1-3/4" |
0.134" |
21/32" |
1-5/16" |
0.095" |
3/4" |
13/16" |
2" |
0.148" |
13/16" |
1-15/32" |
0.134" |
7/8" |
15/16" |
2-1/4" |
0.165" |
15/16" |
1-3/4" |
0.134" |
1" |
1-1/16" |
2-1/2" |
0.165" |
1-1/16" |
2" |
0.134" |
1-1/8" |
1-1/4" |
2-3/4" |
0.165" |
- |
- |
- |
1-1/4" |
1-3/8" |
3" |
0.165" |
- |
- |
- |
1-3/8" |
1-1/2" |
3-1/4" |
0.180" |
- |
- |
- |
1-1/2" |
1-5/8" |
3-1/2" |
0.180" |
- |
- |
- |
1-5/8" |
1-3/4" |
3-3/4" |
0.180" |
- |
- |
- |
1-3/4" |
1-7/8" |
4" |
0.180" |
- |
- |
- |
2" |
2-1/8" |
4-1/2" |
0.213" |
- |
- |
- |
Alloy 20 Washers are used wherever chemical resistance and mechanical reliability are required in bolted assemblies.
Alloy 20 Washers are manufactured using precision cold forging followed by controlled heat treatment to achieve optimal mechanical properties. Each batch undergoes dimensional inspection using calibrated gauges to ensure compliance with DIN and ISO standards. Surface finishing is verified to eliminate micro-defects that could trigger corrosion initiation.
Hardness testing and chemical composition analysis ensure material integrity throughout production. KK Fasteners implements full lot traceability and quality documentation for every shipment, supporting ISO 9001-certified manufacturing systems. Additional testing such as salt spray and corrosion resistance validation is performed for critical export orders, ensuring consistent performance in demanding global applications.
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Alloy 20 washers are corrosion-resistant fastening components made from UNS N08020 nickel-iron-chromium alloy. They are designed to distribute load evenly in bolted joints while resisting sulfuric acid, chloride attack, and other aggressive chemical environments commonly found in industrial processing systems.
They are primarily manufactured from Alloy 20 (UNS N08020), which contains nickel, iron, chromium, copper, and molybdenum. This composition provides superior resistance to acid corrosion, especially sulfuric acid, making them suitable for chemical and marine applications.
Common standards include ASTM B473 for Alloy 20 material, DIN 125 for flat washers, ISO 7089 for dimensional compliance, and ASTM-based fastener specifications depending on application requirements in global industries.
They are used in chemical processing, pharmaceuticals, marine systems, heat exchangers, desalination plants, and oil & gas facilities where resistance to corrosive media and mechanical reliability in bolted joints are essential.
Look for ISO-certified production, material traceability, compliance with ASTM/DIN standards, and proven export capability. Suppliers like KK Fasteners provide certified quality control, testing reports, and global logistics support for industrial buyers.
Engineered for aggressive chemical environments, Alloy 20 Washers ensure long-term fastening reliability where standard alloys fail. With precision manufacturing, certified quality systems, and global supply capability, KK Fasteners supports critical industries with consistent, traceable fastening solutions.
For technical specifications, bulk pricing, or customized requirements, connect with KK Fasteners to request a quote or engineering consultation today.
