Specifications

Composition

Phosphorus and sulphur limits as given in the standards.

Both alloys have very low carbon and silicon, which lets them be welded and used in the as-welded condition without losing corrosion resistance at the weld.

C276 or C22 pipe?

Hastelloy C276 is the most widely used C-type alloy for pipe. Its high molybdenum content gives excellent resistance in reducing acids and chloride-bearing solutions, and it is the standard choice for scrubbers, acid lines and chlorination systems. Hastelloy C22 has more chromium and somewhat less molybdenum, which improves its resistance in oxidising media and in mixed streams that switch between oxidising and reducing conditions – common in pharmaceutical and fine-chemical batch plants. Where the process is a reducing acid such as hydrochloric acid with no oxidising contaminants, nickel-molybdenum alloys B2 or B3 are considered. The final choice should be based on corrosion data for the actual process stream.

Seamless or welded?

Seamless Hastelloy pipe to B622 is supplied in smaller and medium sizes and is preferred for high-pressure or critical lines. Welded pipe to B619 and welded tube to B626 are widely used in larger diameters and thin walls, where they offer lower cost and good availability; they are produced from solution-annealed sheet or strip, welded and then solution annealed, and the welds are tested. ASTM B619 and B626 include classes that define the weld's cold working, heat treatment and examination, which should be stated on the order where the project specifies them.

Quality, documents and ordering

Hastelloy pipes and tubes are tested as their standards require, including a hydrostatic or non-destructive electric test on each length, and are marked with alloy, specification, size and heat number. Intergranular corrosion testing, ultrasonic or eddy-current examination and positive material identification can be added. We verify each consignment against the mill test certificate and order before dispatch, and third-party inspection is available on request.

Please give the alloy and UNS number, seamless (B622) or welded (B619/B626) and class, size and schedule or OD and wall, length, quantity and any supplementary tests.

Fabrication notes

Hastelloy pipe is welded with matching filler metal, low heat input and strict cleanliness. Because the alloys are used in the most aggressive service, weld quality is critical: root oxidation should be prevented with backing gas, and weld bead profiles kept smooth to avoid crevices. Cold bending is possible; hot bending requires re-solution annealing. Keep Hastelloy pipe away from carbon steel contamination during storage and fabrication.

For small-bore instrument and sampling lines in aggressive service, seamless Hastelloy tube is often used with compression fittings made from the same alloy.

Applications and related products

Hastelloy pipes and tubes are used in chemical and pharmaceutical reactors and transfer lines, acid and chlorine plants, pulp and paper bleaching, flue gas desulphurisation, waste incineration and sour gas service. They are installed with Hastelloy pipe fittings, Hastelloy flanges and Hastelloy fasteners. We also supply Hastelloy sheets and plates and Hastelloy round bars. Alloy guidance is on the Hastelloy page, and other seamless materials on the seamless pipes and tubes page.