Hastelloy C276 Fasteners: Properties, Standards, Uses and Buying Guide

A flange is only as reliable as the bolts holding it together. In plants that handle hot acids, wet chlorine or chloride-rich process streams, a stainless steel bolt can corrode and fail long before the pipe it clamps. That is why engineers specify Hastelloy C276 fasteners for the joints that cannot be allowed to leak. This guide explains what the alloy is, what its fasteners can and cannot do, which standards apply, and what to confirm before you place an order.

What is Hastelloy C276?

Hastelloy C276 (UNS N10276, Werkstoff 2.4819, also written Alloy C276) is a nickel-molybdenum-chromium alloy with a small tungsten addition. Nickel makes up the balance, at roughly 57%. Molybdenum and chromium give it resistance to both reducing and oxidising environments, which is unusual, because most alloys favour one or the other. Very low carbon and silicon keep carbide precipitation in the weld zone to a minimum, so welded equipment can generally be used without a post-weld solution anneal.

Chemical composition

Some older data sheets show 0.02% carbon. Check the limit in the edition of the standard named on your order.

Typical properties

These are typical values for annealed material, not guaranteed minimums. Specification minimums are set in ASTM B574, so check the current edition.

For fasteners, one point matters more than any table. C276 is not heat-treatable, so its strength rises with cold work. One wire data sheet shows yield strength climbing from 455 MPa with no cold work to 1310 MPa at 40% cold work, while elongation drops from 40% to under 4%. Cold-formed bolts and rolled threads can therefore be stronger than annealed bar, but strength varies with size and process. State the strength you need on the order instead of assuming a figure.

Why choose C276 fasteners?

• Wet chlorine, hypochlorite and chlorine dioxide: C276 is one of the few materials that withstands them, which is why it appears in pulp bleaching and chlor-alkali plants.
• Strong oxidising chlorides: it resists ferric and cupric chloride solutions that destroy stainless steel.
• Pitting, crevice attack and stress corrosion cracking: the molybdenum content gives high resistance, which matters at flange faces and under washers where crevices form.
• Sulphuric acid and flue gas scrubbers: it is widely used in sulphuric acid equipment and in flue gas desulphurisation systems, where chlorides and sulphur compounds combine.
• High temperature oxidation: the alloy resists oxidising atmospheres up to about 1038 °C. For load-bearing fasteners, the design code sets a much lower working limit, so check the allowable stress at your operating temperature.

Fastener types and how they are made

Hindco Steel and Alloys lists Hastelloy C276 fasteners in these forms:

• Bolts, including hex and square head
• Nuts
• Studs and threaded rods
• Screws
• Washers
• Custom parts made to your drawing, including German, Italian, British and American specifications

Small sizes are usually cold forged, larger sizes are hot forged, and special or low-volume parts are machined on CNC equipment. The product page lists BSW, UNC, BSF, UNF and metric threads, and head drives including six-lobe, Phillips and slotted.

Standards and designations you will see

• ASTM B574 / ASME SB574: nickel-molybdenum-chromium alloy rod, the usual source specification for fasteners cut or formed from bar.
• ASTM B564 / ASME SB564: forgings, which apply to hot-forged parts.
• ASME B18.2.1 and B18.2.2: dimensions of hex bolts, screws and nuts.
• ASME B1.1: unified inch screw threads (UNC and UNF).
• DIN and ISO standards: common for metric fasteners and European drawings.
• UNS N10276, W.Nr 2.4819, Alloy C276: designations for the alloy.

Name the material standard, the dimensional standard and the thread on every enquiry, for example "hex bolt to ASME B18.2.1, UNC thread, ASTM B574 UNS N10276".

Where Hastelloy C276 fasteners are used

• Chemical and petrochemical plants: reactors, heat exchangers, pressure vessels and acid service.
• Pollution control: flue gas desulphurisation scrubbers and waste treatment.
• Pulp and paper: bleach plants and chlorine-related service.
• Oil and gas: sour gas, offshore and subsea equipment.
• Power generation: thermal and nuclear plants.
• Marine and desalination: equipment exposed to hot, chloride-rich water.

C276 compared with other alloys

If your process chemistry is not fully known, ask your process engineer or the end user for the corrosion data before you finalise the alloy. A wrong fastener grade is cheap to prevent and costly to replace.

Installation and handling tips

• Use a suitable thread lubricant. Nickel alloys can gall when tightened, so choose a lubricant approved for the service and avoid fast, high-torque tightening.
• Control torque. Strength depends on how the fastener was made, so tighten to the value specified for that material and size.
• Match materials. Check the flange and equipment metal, since mixing metals can create galvanic corrosion.
• Keep it clean. Store C276 away from carbon steel, and use clean tools, to avoid surface contamination.

How to buy Hastelloy C276 fasteners: a checklist

Before you order, confirm these points with your supplier:

1. Material and standard: UNS N10276 to ASTM B574 or ASME SB574, plus B564 for forged parts.
2. Fastener type and dimensional standard: for example hex bolt to ASME B18.2.1, or your own drawing.
3. Size and thread: diameter, length, thread type and fit class.
4. Manufacturing route and condition: cold forged, hot forged or machined, and whether you need annealed or cold-worked strength.
5. Chemistry: a heat-wise chemical report, with carbon at or below the specified limit.
6. Certificates: a mill test certificate that shows the heat number, chemistry and mechanical results, in the certificate type your project requires.
7. Testing: positive material identification on the lot, hardness, dimensional checks, and third-party inspection if your contract needs it. Hindco states that every batch is checked, so ask which tests and reports come with your order.
8. Marking and packing: grade and heat markings on each lot, clean packing kept apart from carbon steel, and protection for the threads.
9. Quantity and lead time: whether the size is in stock or must be forged or machined.

Prices follow nickel and molybdenum market rates, and also depend on size, quantity, manufacturing route, testing and certification, so ask for a current quote rather than relying on an old price list.

Get a quote for Hastelloy C276 fasteners

Send us the fastener type, size, thread, material standard, quantity, certificate requirement and delivery country, with your drawing if you have one, and our team will prepare a quote for your requirement.

• Email: info@hindco.co.in
• Phone and WhatsApp: +91-9619035659
• Product page: Hastelloy C276 fasteners at Hindco Steel and Alloys