Patriot Bolt machines Alloy 20 stud bolts from certified ASTM B473 bar (UNS N08020). Alloy 20 is a nickel-iron-chromium alloy with copper and molybdenum, developed for sulfuric acid service, and it resists chloride stress corrosion cracking.
We make Alloy 20 studs to your purchase order or drawing and supply matching Alloy 20 heavy hex nuts. Every order ships with mill test reports traceable to the heat.
Alloy 20 Stud Bolts at a Glance
- Material
- Alloy 20, UNS N08020
- Bar specification
- ASTM B473 / ASME SB473
- Strength
- 80 ksi min tensile, 35 ksi min yield (annealed)
- Key elements
- 32–38% Ni, 19–21% Cr, 3–4% Cu, 2–3% Mo
- Matching nut
- Alloy 20 heavy hex
- Configurations
- Fully threaded, double-end and tap-end
Why Engineers Specify Alloy 20 Studs
- Sulfuric acid resistance. Copper and molybdenum help Alloy 20 resist sulfuric acid across a wide range of concentrations.
- Chloride stress corrosion cracking. High nickel content gives much better resistance than 304 or 316 stainless.
- Stabilized. Niobium ties up carbon, which limits sensitization during welding of nearby equipment.
- Matched joint. Alloy 20 nuts on Alloy 20 studs avoid galvanic mismatch in corrosive service.
Alloy 20 Stud Bolt Specifications
ASTM B473 sets minimum properties by condition.
| Condition | Tensile, min | Yield (0.2%), min | Elongation, min | Reduction of area, min |
|---|---|---|---|---|
| Annealed, all sizes | 80 ksi | 35 ksi | 30% | 50% |
| Annealed and strain hardened, to 2 in | 90 ksi | 60 ksi | 15% | 40% |
Annealed Alloy 20 is lower in strength than alloy steel bolting. Check preload and torque with your engineer.
Alloy 20 Chemical Composition
| Element | Weight % |
|---|---|
| Nickel | 32.0–38.0 |
| Chromium | 19.0–21.0 |
| Copper | 3.0–4.0 |
| Molybdenum | 2.0–3.0 |
| Niobium + tantalum | 8 × C min, 1.00 max |
| Manganese | 2.00 max |
| Silicon | 1.00 max |
| Carbon | 0.07 max |
| Phosphorus | 0.045 max |
| Sulfur | 0.035 max |
| Iron | Balance |
Limits per the current edition of the specification. The mill test report for your heat is the controlling document.
Stud Configurations
- Fully threaded studs, threaded end to end, for flange bolting where grip length varies.
- Double-end studs, threaded on both ends with an unthreaded center.
- Tap-end studs, with one end made to thread into a tapped hole.
Applications and Industries
- Chemical processing: Sulfuric, phosphoric and nitric acid piping, pumps and valves. See Petrochemical & Refining.
- Pickling and metal finishing: Acid tanks and process lines. See Industrial Manufacturing.
- Pharmaceutical and specialty chemicals: Flanged equipment in corrosive service.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each Alloy 20 order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification on your purchase order.
Studs are marked with the grade symbol and our identification, as the specification requires.
Compare Alloy 20 with other bolting grades in our Fastener Materials Matrix.
Alloy 20 Stud Bolts FAQ
What is Alloy 20 used for?
Mainly sulfuric acid service, plus other acids and chloride-bearing process streams where 316 stainless does not hold up.
Is Alloy 20 a stainless steel?
It is often grouped with stainless steels, but with 32 to 38 percent nickel it is classed as a nickel-iron-chromium alloy.
What specification covers Alloy 20 bar for studs?
ASTM B473 / ASME SB473 covers UNS N08020 bar and wire.
Can you make Alloy 20 studs to my drawing?
Yes. We machine Alloy 20 studs in any diameter, length and thread from your drawing or purchase order.
Request a Quote
Send us the stud configuration, diameter, length, thread, specification and quantity, or upload your drawing. Our team will confirm the material and lead time. Call (281) 581-0176 or request a quote.
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