Alloy 660 Bolts and Fasteners (Trade Name for A286 / UNS S66286)
Alloy 660 is the international commercial trade name for the bolting material specified by ASTM A453 Grade 660 and by SAE / AMS as A286 (UNS S66286). Procurement engineers in Europe, the Middle East, and Asia who shop by trade name rather than UNS code or ASTM designation search for Alloy 660 bolts, Alloy 660 studs, and Alloy 660 fasteners; the technical fastener is the same iron-nickel-chromium precipitation-hardening austenitic stainless steel superalloy regardless of the name used on the procurement requisition. This page is the cross-reference from the trade-name search to the underlying A286 material data, the governing ASTM A453 Grade 660 standard, and the bolting product family.
Alloy 660 = A286 Designation Cross-Reference
| Designation System | Code | Comment |
|---|---|---|
| UNS | S66286 | Universal Numbering System (joint SAE / ASTM) |
| ASTM Bolting | A453 Grade 660 (Classes A, B, C, D) | ASME BPVC pressure-vessel bolting |
| ASTM Bar | A638 Grade 660 | Bar for non-bolting applications |
| AMS (Aerospace) Bar Sol+Aged | AMS 5732 | Solution treated and precipitation aged |
| AMS Precision Bar (Cold-Heading) | AMS 5737 | Tight dim and HT tolerance |
| AMS Sol-Treated | AMS 5731 | Solution treated only (forming feedstock) |
| DIN | 1.4980 (X5NiCrTiMoVB25-15-2) | German equivalent |
| JIS | SUH 660 | Japanese equivalent |
| AISI | 660 | Older AISI designation, still seen |
| Trade Name | Alloy 660 / Iron Alloy 660 | Common procurement search term |
| Brand Names | Pyromet 660, Carpenter A-286, ATI A286 | Mill-specific brand naming |
All entries above refer to the same iron-nickel-chromium superalloy. The choice of designation depends on the specifying engineer, country, and standard system.
Alloy 660 Nominal Chemistry (per ASTM A453 Table 1, Grade 660)
| Element | Min % | Max % | Role |
|---|---|---|---|
| Iron (Fe) | (balance, ~53%) | (balance) | Matrix metal |
| Nickel (Ni) | 24.0 | 27.0 | Austenite stabiliser |
| Chromium (Cr) | 13.5 | 16.0 | Oxidation resistance |
| Titanium (Ti) | 1.90 | 2.35 | Gamma-prime former |
| Molybdenum (Mo) | 1.00 | 1.50 | Solid-solution strengthener |
| Manganese (Mn) | , | 2.00 | Deoxidiser |
| Vanadium (V) | 0.10 | 0.50 | Carbide refinement |
| Aluminium (Al) | , | 0.35 | Co-former of gamma-prime |
| Boron (B) | 0.001 | 0.010 | Grain-boundary strengthener |
| Carbon (C) | , | 0.08 | Carbide former |
Chemistry per ASTM A453 Table 1 for Grade 660. Same chemistry applies under any of the trade-name or designation aliases for the alloy.
Alloy 660 Bolting Product Forms (per ASTM A453 8.x)
| Product Form | Typical Spec | Standard Sizes |
|---|---|---|
| Hex Bolts (heavy and standard) | A453 Grade 660 Class B, C, or D | 1/4 in to 4 in, M6 to M100 |
| Stud Bolts (double-end, full-thread) | A453 Grade 660 Class B, C, or D | 1/4 in to 4 in, M6 to M100 |
| Socket Head Cap Screws | AMS 5737 (precision) or A453 | 8-32 UNC to 1-8 UNC |
| Nuts (heavy hex, jam, lock) | A453 Grade 660 matched to bolt class | 1/4 in to 4 in, M6 to M100 |
| Washers (flat, lock) | AMS 5732 or A453 | 1/4 in to 2 in, M6 to M48 |
| Threaded Rod (all-thread) | A453 Grade 660 Class B | 1/4 in to 2 in, M6 to M48 |
Standard Alloy 660 bolting product forms are supplied to ASTM A453 for pressure-vessel and bolted-joint applications. Aerospace AMS-spec callouts are used where the receiving drawing references AMS 5737 cold-headed feedstock.
Typical Applications
Alloy 660 bolts and fasteners are specified globally for high-temperature high-strength bolted joints: ASME B16.5 pressure-vessel flange bolting, gas-turbine combustor casing bolting, jet-engine bearing support hardware, nuclear pressure-boundary internals (per ASME Section III where A453 Grade 660 Class B or D is the standard callout), offshore wellhead bolting, refinery high-temperature service, and any application demanding both 700 degree C service capability and 304-stainless-equivalent corrosion resistance in a single non-magnetic alloy. The trade name Alloy 660 dominates European and Middle East procurement nomenclature; the equivalent A286 / UNS S66286 dominates US aerospace procurement nomenclature.
Frequently Asked Questions
Is Alloy 660 the same as A286?
Yes. Alloy 660 is the international commercial trade name for the bolting and bar material specified by ASTM A453 Grade 660 and by SAE / AMS as A286 (UNS S66286). The chemistry, mechanical properties, and heat-treatment requirements are identical regardless of which name appears on the procurement document. Other equivalents include DIN 1.4980 (X5NiCrTiMoVB25-15-2), JIS SUH 660, AISI 660, and brand names Carpenter A-286, Pyromet 660, and ATI A286.
Why are some materials called Alloy 660 instead of A286?
Naming follows where the specifying engineer trained. European and Asian procurement teams that learned material codes from BS / DIN / JIS standards typically use Alloy 660 or AISI 660 in requisitions. US aerospace engineers trained on AMS / SAE codes use A286 or AMS 5737. US pressure-vessel engineers trained on ASTM use A453 Grade 660. The international commercial trade name Alloy 660 bridges all three communities and is what appears in trade-show catalogues, distributor inventory listings, and global B2B marketplaces.
What is the difference between Alloy 660 and Inconel 718?
Both are precipitation-hardening superalloys but the base metal differs. Alloy 660 is iron-base (53 percent Fe, 25 percent Ni nominal), with serviceable strength to 700 degree C, at a price point roughly half of nickel-base equivalents. Inconel 718 is nickel-base (52 percent Ni, 19 percent Cr, 18 percent Fe), with serviceable strength to 700-750 degree C, at higher cost. Alloy 660 is the cost-and-strength sweet spot for high-temperature bolting from cryogenic to 700 degree C; Inconel 718 takes over above 700 degree C where the iron-base superalloy loses gamma-prime stability.
Is Alloy 660 magnetic?
No. Alloy 660 is non-magnetic with relative magnetic permeability of approximately 1.005 in the precipitation-aged condition. The underlying austenitic face-centred-cubic structure is retained through aging, preserving the non-magnetic behaviour. This qualifies Alloy 660 for use in instrument housings, magnetic-resonance imaging hardware, and other electromagnetic-sensitive applications where ferritic alloy-steel fasteners would distort the field.
Related A286 Products and Specifications
Cross-reference to the broader A286 material data: A286 equivalent grades cross-reference, ASTM A453 Grade 660 standard, ASTM A638 Grade 660 bar standard, UNS S66286 designation, A286 chemical composition, A286 mechanical properties, DIN 1.4980 X5NiCrTiMoVB25-15-2 equivalent.
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