Alloy 20 Fasteners: Bolts, Nuts, Stud Bolts & Washers (UNS N08020)
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Grade: Alloy 20 / Carpenter 20 · UNS N08020 · Standards: ASTM B473, B462, F468 · Types: Bolts · Nuts · Stud Bolts · Hex Bolts · Washers · 100% PMI
Aashish Metals offers Alloy 20 bolts, nuts, washers, stud bolts and hex bolts that are used in a bolted joint where the bolt must withstand sulphuric acid. The most frequently requested items are alloy 20 nuts and stud bolts and all ships with a mill test certificate and positive material identification. This page is part of our full Alloy 20 products range, so a complete acid service assembly can be obtained from one grade from one supplier.
Also known as Carpenter 20, alloy 20 is a nickel-iron-chromium alloy with an addition of copper and molybdenum, designed for use in sulphuric acid in a full spectrum of concentrations and temperatures, where normal 316 stainless steel corrodes. To this end, it is selected for fasteners in acid plant, pickling lines, chemical processing and of course the matching Alloy 20 instrumentation ball valves and fittings built to complete the line. Provide type, size and quantity, and the quote is returned with certification included.
ASTM B473 Alloy 20 Stud Bolts, UNS N08020 Fasteners, Incoloy® alloy 20 Socket Head Cap Screws, DIN 2.4660 Studs, Alloy 20 Industrial Fasteners Suppliers in Mumbai, India.
Alloy 20 Fastener Types We Supply
| Type | Details | Common standards |
|---|---|---|
| Nuts | Hex nuts, heavy hex nuts, lock nuts and coupling nuts, the most-requested Alloy 20 item | ASTM A194, dimensions to ASME B18.2.2 |
| Stud bolts & studs | Fully threaded stud bolts and tap-end studs with matching nuts for flange joints | ASTM B473 / A193 style, ASME B16.5 flanges |
| Bolts & hex bolts | Hex head bolts, heavy hex structural bolts | ASME B18.2.1 |
| Washers | Flat washers, spring and heavy washers to suit the bolting | ASME B18.22.1 |
| Screws & socket screws | Machine screws, socket head cap screws, set screws | To order |
| Threaded rod | Continuous threaded rod in Alloy 20 for cut-to-length studs | UNC / metric |
Alloy 20 Specification & Composition
| Property | Value |
|---|---|
| Common names | Alloy 20, Carpenter 20, 20Cb-3 |
| UNS number | N08020 |
| Fastener standards | ASTM B473 (bar/wire for fasteners), ASTM B462 (bolting flanges), ASTM F468 (nonferrous bolts) |
| Nominal composition | Nickel 32-38%, chromium 19-21%, iron balance, copper 3-4%, molybdenum 2-3%, plus niobium stabilisation |
| Key feature | Copper and molybdenum for sulphuric acid resistance; niobium stabilised against sensitisation |
| Density | About 8.05 g/cm3 |
| Certification | EN 10204 3.1 mill test certificate, PMI, NACE MR0175 on request |
Why Alloy 20 for Fasteners: Sulphuric Acid
Alloy 20 was designed around one problem: sulphuric acid attacks stainless steel, and Alloy 20’s copper and molybdenum give it resistance across a wide band of sulphuric acid concentration and temperature that 316 cannot match. It also resists chloride stress-corrosion cracking better than standard austenitic stainless, and handles phosphoric acid and many mixed acids. For a bolted joint in acid service, that means the fastener lasts as long as the equipment instead of becoming the first thing to fail. Choosing it is a matter of matching the duty: below acid service, 316/316L stainless fasteners are the cheaper and correct answer; where the acid is stronger, hotter or contaminated beyond what Alloy 20 covers, the step up is Incoloy 825, its close cousin, or a Hastelloy grade. Alloy 20 sits in the sweet spot for sulphuric acid specifically, which is exactly why it is specified by name.
Standards & Sizes
Alloy 20 fasteners are supplied to the recognised bolting standards, in imperial and metric threads:
- Material standards: ASTM B473 for the bar and wire, ASTM B462 for flange bolting, ASTM F468 for nonferrous bolts and studs.
- Dimensional standards: ASME B18.2.1 for bolts, B18.2.2 for nuts, B18.22.1 for washers.
- Threads: UNC, UNF and metric coarse, cut or rolled, with matching nuts supplied to the same grade.
- Sizes: common stud and bolt sizes from small diameters up to large flange bolting, with special sizes and lengths made to order.
Related Types Of Alloy 20 Bolts
Alloy 20 Bolts
Alloy 20 Nuts
Alloy 20 Stud Bolts
Alloy 20 Washers
Alloy 20 Screw
Alloy 20 Anchor Bolts
Alloy 20 Threaded Rod
Alloy 20 Hex Bolts
Complete the Assembly in Alloy 20
Fasteners are one part of an acid-service line, and a mixed-metal joint is a weak joint, so we hold the matching forms in the same grade under the Alloy 20 products range: instrumentation ball valves, needle valves, manifold valves, tube fittings and buttweld pipe fittings. Specifying the bolting, valves and fittings together in Alloy 20 keeps the whole line to one corrosion grade and one certificate trail.
Quality, Certification & PMI
Every Alloy 20 fastener ships with an EN 10204 3.1 mill test certificate, heat-number traceable, with positive material identification available piece by piece so an Alloy 20 nut is confirmed as N08020 and not a look-alike stainless. Mechanical and hardness testing to the fastener standard, NACE MR0175 documentation for sour service, and third-party witness through BV, SGS or TUV are arranged at order stage. Standard nuts, stud bolts and washers in common sizes ship quickly; special sizes and full assemblies are confirmed on enquiry. Send the type, the size and the quantity and the quote comes back with the certification built in.
Alloy 20 Fasteners: Frequently Asked Questions
Bolts, nuts, stud bolts, hex bolts, washers, screws and threaded rod in UNS N08020, with nuts and stud bolts the most-requested items. They are supplied to ASTM B473, B462 and F468 with dimensions to the ASME B18 standards, in imperial and metric threads. Special sizes and lengths are made to order.
Alloy 20, also called Carpenter 20 and UNS N08020, is a nickel-iron-chromium alloy with copper and molybdenum, designed specifically to resist sulphuric acid where stainless steel corrodes. In a bolted joint in acid service, an Alloy 20 fastener lasts as long as the equipment rather than becoming the first point of failure, which is why it is specified for acid plant, pickling and chemical processing bolting.
Sulphuric acid resistance. 316 stainless is the economical choice for general corrosion, but sulphuric acid attacks it, whereas Alloy 20’s copper and molybdenum give it resistance across a wide band of sulphuric acid concentration and temperature. Use 316 below acid service and Alloy 20 where sulphuric acid is present. Where the acid exceeds what Alloy 20 handles, Incoloy 825 or a Hastelloy grade is the next step.
The material is supplied to ASTM B473 for bar and wire, ASTM B462 for flange bolting and ASTM F468 for nonferrous bolts and studs, with dimensions to ASME B18.2.1 for bolts, B18.2.2 for nuts and B18.22.1 for washers. Threads are UNC, UNF or metric, and matching nuts are supplied in the same grade.
Yes, on every order. Each ships with an EN 10204 3.1 mill test certificate that is heat-number traceable, with positive material identification piece by piece, mechanical and hardness test reports to the fastener standard, and NACE MR0175 documentation and third-party witness inspection available at order stage.
For More Information About Alloy 20 Fasteners please call +91-22-66362223 / 66394926 or send an email to export@aashishmetal.com
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