Hastelloy B2
Fasteners
UNS N10665
Hastelloy B2 — 62% Ni · 28% Mo Reducing Acid Alloy
Hastelloy B2 (UNS N10665) is a Ni-Mo binary alloy — approximately 62% Ni with 26–30% Mo and strictly limited iron (≤2%) and cobalt (≤1%). The absence of chromium is deliberate: B2 is optimised purely for reducing acid environments where chromium adds no benefit, and the very high molybdenum content (second only to B3 in the B-series) gives B2 outstanding immunity to HCl at all concentrations and temperatures, reducing H₂SO₄, acetic acid, and phosphoric acid. In these environments, B2 outperforms all austenitic stainless steels, all duplex grades, and even Ni-Cr-Mo alloys like C276.
The critical limitation of B2 versus its successor Hastelloy B3 (UNS N10675): B2 is susceptible to knife-line attack and heat-affected zone corrosion adjacent to welds — a precipitation of Ni₄Mo at intermediate temperatures (200–650°C) during slow cooling sensitises the grain boundaries. B3 was developed specifically to eliminate this sensitisation tendency through the addition of titanium and improved composition controls. For new project design and greenfield construction, B3 is now the preferred reducing acid alloy. B2 remains fully specified in maintenance procurement, replacement fasteners for existing B2-fitted equipment, and in markets where B2 specifications are contractually mandated.
Akbar Fasteners Pvt. Ltd. supplies B2 fasteners from ASTM B335 certified UNS N10665 solution-annealed bar. Every lot PMI-verified before production. Full MTC, COC, NABL test reports. Matched B2 hex nuts and washers from same certified heat available.
| Element | Min % | Max % | Typical |
|---|---|---|---|
| Nickel (Ni) | Balance | — | ~62% |
| Molybdenum (Mo) | 26.0 | 30.0 | ~28% |
| Iron (Fe) | — | 2.0 | ~1% |
| Cobalt (Co) | — | 1.0 | — |
| Chromium (Cr) | — | 1.0 | — |
| Manganese (Mn) | — | 1.0 | — |
| Carbon (C) | — | 0.02 | — |
| Silicon (Si) | — | 0.10 | — |
Hastelloy B2 Fasteners — All Product Forms
All forms manufactured from ASTM B335 certified UNS N10665 solution-annealed bar. PMI-verified before production. Matched assemblies from same certified heat — one MTC, one PMI, one COC.
B2 Stud Bolts
Fully threaded and equal-end double stud configurations to ASME B16.5. Class 150–2500. M12–M100, lengths to 3,000mm. Primary B2 fastener for ASME flanged pressure joints in HCl piping, HF acid lines, and reducing H₂SO₄ process equipment. Matched B2 heavy hex nuts from same heat on request.
B2 Hex Bolts
Full thread (DIN 933), partial thread (DIN 931), and heavy hex (ASME B18.2.3.6M) in B2 for chemical equipment cover bolts, reactor body connections, and acid plant structural bolting in reducing acid environments. M6–M100. For flanged joints see B2 stud bolts.
B2 Hex Nuts
Standard hex (DIN 934), heavy hex (ASME B18.2.2), and coupling nuts (DIN 6334) in UNS N10665. M6–M100. Matched material from same ASTM B335 certified heat as stud bolts — same-heat assembly for HCl, H₂SO₄ reducing, and acetic acid service eliminates galvanic corrosion at the nut bearing face.
B2 Washers
Plain flat (DIN 125 A/B) and spring helical (DIN 127) in B2 UNS N10665. M5–M100. Same-heat as stud bolts — zero galvanic potential at the washer-nut bearing interface in HCl, reducing H₂SO₄, and acetic acid flange assemblies.
B2 Threaded Rods
Full thread DIN 975 and end-thread DIN 976. M6–M100, lengths to 3,000mm. For HCl plant equipment hanger systems, acid storage tank tie-rods, and reducing acid process equipment support structures. Cut-to-length service available on request to sales@akbarfasteners.in.
Socket Cap Screws
Hex socket cylindrical head in B2 UNS N10665 for confined-access bolting in chemical reactor internals, acid plant instrument enclosures, and HCl scrubber internal fixtures where hex head clearance is unavailable. M4–M36. Same ASTM B335 certified material.
Hastelloy B2 vs Hastelloy B3 — When to Specify Each
Both B2 (N10665) and B3 (N10675) are Ni-Mo alloys for reducing acid service. The selection between them is determined by fabrication context, sensitisation risk, and project specification history. Both grades are available from Akbar Fasteners Pvt. Ltd. from the same ISO 9001:2015 certified Mumbai facility.
Hastelloy B2 (UNS N10665)
Hastelloy B3 (UNS N10675)
Standards We Manufacture & Test To
Same quality system as our Hastelloy B3 stud bolts and complete ASTM B574 Hastelloy fastener range. Full heat traceability from mill certificate to dispatch.
Industry Applications
Reducing acid environments where stainless steels, duplex grades, and even Ni-Cr-Mo alloys fail — and where existing equipment is specified to UNS N10665 requiring B2 replacement fasteners.
HCl Gas Plant
hydrochloric acid storage
Chemical Processing
H₂SO₄ dilute service
HF Acid Systems
alkylation unit piping
Acetic Acid Plant
acetic anhydride systems
Phosphoric Acid
fertiliser plant flanges
Acid Recovery
spent acid reconcentration
Pharmaceutical
HCl reaction equipment
Oil Refining
crude oil acidising
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · Hardness
TÜV · BV · Lloyds
Compare B2, B3 & Hastelloy Grades
B2 for existing equipment replacement. B3 for new design. Hastelloy C-series for mixed or oxidising + reducing media.
Hastelloy B3 Stud Bolts
The current-generation Ni-Mo alloy preferred for new reducing acid projects. Eliminates B2’s sensitisation risk. Near-zero corrosion in HCl at all concentrations. ASME B16.5 Class 150–2500.
View Page →ASTM B574 Hastelloy Fasteners
Full Hastelloy C-series for mixed acid service where B2’s reducing-acid-only coverage is insufficient. C276 for mixed oxidising + reducing media. All product forms.
View All Grades →Hastelloy Fasteners India
Complete Hastelloy range — all six grades as bolts, studs, nuts, washers from ISO 9001:2015 certified Mumbai facility. Grade selection guidance. Export to 50+ countries.
View Range →Hastelloy C276 Stud Bolts
For mixed oxidising + reducing acid service where B2 is not specified — C276’s 16% Mo covers both reducing and oxidising environments. ASME B16.5 Class 150–2500.
View Page →Need Hastelloy B2
Fasteners Now?
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