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Product Overview
Alloy 20 (Carpenter 20Cb-3) threaded rods are high-performance austenitic nickel-iron-chromium alloy fasteners designed for exceptional resistance to sulfuric acid and chloride-induced stress corrosion cracking. Manufactured from UNS N08020 bar stock per ASTM B473, these rods are stabilized with niobium (columbium) to prevent sensitization and intergranular corrosion, making them ideal for chemical processing and pharmaceutical industries.
Alloy 20 threaded rods are widely specified for use in acid storage tanks, process piping, and equipment where standard stainless steels such as 304 or 316L fail due to aggressive corrosion. Their unique composition provides superior resistance to pitting, crevice corrosion, and stress corrosion cracking in harsh environments.
| Material | Alloy 20 (Carpenter 20Cb-3) |
| UNS Number | N08020 |
| DIN Number | 2.4660 |
| Material Standard | ASTM B473 |
| Rod Standard (Metric) | DIN 976 / ISO 898-1 |
| Rod Standard (Inch) | ASME B18.31.3 |
| Thread Form | ISO Metric / UNC / UNF |
| Diameter Range | M6-M64 / ¼"-2½" |
| Tensile Strength | 551 MPa (80 ksi) min |
| Yield Strength | 241 MPa (35 ksi) min |
| Hardness | Max 217 HB |
Complete the Fastener Set
Technical Data
| Size (M) | Pitch (mm) | Rod Dia (mm) | Min L (mm) | Max L (mm) |
|---|---|---|---|---|
| M6 | 1.0 | 6.0 | 100 | 2000 |
| M8 | 1.25 | 8.0 | 100 | 2000 |
| M10 | 1.5 | 10.0 | 100 | 2000 |
| M12 | 1.75 | 12.0 | 100 | 2000 |
| M16 | 2.0 | 16.0 | 100 | 3000 |
| M20 | 2.5 | 20.0 | 100 | 3000 |
| M24 | 3.0 | 24.0 | 100 | 3000 |
| M30 | 3.5 | 30.0 | 100 | 3000 |
| M36 | 4.0 | 36.0 | 100 | 3000 |
| M42 | 4.5 | 42.0 | 100 | 3000 |
| M48 | 5.0 | 48.0 | 100 | 3000 |
| M56 | 5.5 | 56.0 | 100 | 3000 |
| M64 | 6.0 | 64.0 | 100 | 3000 |
| Standard | Covers | Thread |
|---|---|---|
| DIN 976 | Threaded rods, metric | Metric |
| ASME B18.31.3 | Threaded rods, inch | UNC/UNF |
| ISO 898-1 | Mechanical properties | Metric |
| ASTM A193 | High temp/pressure rods | UNC |
| Material Standard | Requirement |
|---|---|
| ASTM B473 | Bar/rod - UNS N08020 |
| ASTM B462 | Forgings |
| ASTM F468 | Fastener mechanical |
| EN 10204 3.1 | Mill test certificate |
| EN 10204 3.2 | TPI-witnessed MTC |
Material Chemistry
| Element | Composition (%) |
|---|---|
| Nickel (Ni) | 32.0-38.0% |
| Chromium (Cr) | 19.0-21.0% |
| Iron (Fe) | Balance |
| Copper (Cu) | 3.0-4.0% |
| Molybdenum (Mo) | 2.0-3.0% |
| Manganese (Mn) | 2.0% max |
| Silicon (Si) | 1.0% max |
| Carbon (C) | 0.07% max |
| Niobium (Nb) | 8xC min, 1.0% max |
| Phosphorus (P) | 0.045% max |
| Sulfur (S) | 0.035% max |
Fastener Performance
| Rod Size | Dry (Nm) | Lubricated (Nm) | Clamp Load (kN) |
|---|---|---|---|
| M12 | 62 | 50 | 23 |
| M16 | 150 | 120 | 48 |
| M20 | 295 | 236 | 75 |
| M24 | 510 | 408 | 108 |
| M30 | 1020 | 816 | 174 |
| M36 | 1780 | 1424 | 251 |
| M42 | 2840 | 2272 | 344 |
| M48 | 4220 | 3376 | 452 |
Industry Applications
Alloy 20 threaded rods are the industry standard for sulfuric acid storage tanks, acid piping, and process equipment fastenings. Their resistance to sulfuric, phosphoric, and nitric acids makes them ideal for chemical plant construction and maintenance.
Used in process piping, reactors, and equipment where resistance to organic and inorganic acids is critical, and where contamination from corrosion products must be avoided. Alloy 20 is FDA-accepted for food contact.
Threaded rods for seawater intake structures, desalination plant piping, and marine chemical dosing systems where pitting and crevice corrosion resistance is required beyond 316L capabilities.
Fastening of bleach plant equipment, digesters, and chemical recovery systems exposed to acidic and chloride-rich environments. Alloy 20 rods prevent premature failure and costly downtime.
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