Specifications

Chemical composition and mechanical properties

Alloy 800HT also requires Al + Ti 0.85–1.20%. Alloys 800H and 800HT have grain size and heat-treatment requirements for elevated-temperature service, as given in the standards.

Values common to ASTM B407, B409 and B408 (alloy 800 family), B423, B424 and B425 (alloy 825) and B564 forgings; check the standard for the product form and size.

Background, equivalents and other product forms are on the Incoloy page.

Incoloy 800H and 800HT pipes for high temperatures

Above about 600 °C, piping design is governed by creep and rupture strength rather than tensile strength. Incoloy 800H and 800HT have a controlled carbon content, a solution anneal at high temperature and a coarse grain size, which together give much higher creep strength than alloy 800. They also resist oxidation, carburisation and nitriding. Typical uses are steam methane reformer outlet pigtails and manifolds, hydrogen and syngas transfer lines, ethylene cracking furnace components, superheater and reheater tubing, and heat-treatment furnace parts. Pipe is often dual certified 800H/800HT.

Alloy 800 in the annealed condition, with a finer grain, is used for heat exchangers and process piping below about 600 °C, and for electric heating-element sheathing.

Incoloy 825 pipes and tubes for corrosion

Incoloy 825 contains about 40% nickel, 21% chromium, 3% molybdenum and 2% copper, stabilised with titanium. This composition resists sulphuric and phosphoric acids, chloride stress corrosion cracking, pitting and crevice corrosion, and intergranular attack after welding. Incoloy 825 tubes are used in heat exchangers cooled by seawater or brackish water, in sulphuric acid and pickling plants, phosphoric acid evaporators and pollution-control systems. In oil and gas, 825 is used for downhole tubing, flowlines and the corrosion-resistant layer of clad and lined pipe for sour, wet gas.

Seamless or welded

Seamless Incoloy pipe and tube are used for high-pressure, high-temperature and critical lines, and for heat-exchanger tubes that will be expanded into tube sheets. Welded pipe and tube, made from strip or plate and fully heat treated, are used in thinner walls and larger diameters where they are more economical. The project specification normally states which form is acceptable.

Testing

Each length of pipe or tube is hydrostatically or non-destructively electric tested, as the specification requires. For 800H and 800HT, the mill test certificate also reports grain size, which must meet the minimum the specification sets for creep strength. Supplementary tests such as ultrasonic testing, intergranular corrosion testing for 825, and positive material identification can be added to the order.

Ordering Incoloy pipes and tubes

Please give the alloy, specification, seamless or welded, outside diameter or nominal size, wall thickness or schedule, length, condition, end finish, quantity and any supplementary tests or inspection. Pipes and tubes are packed in wooden boxes with end caps, and each length is marked with alloy, specification, size and heat number.

Applications and related products

Incoloy pipes and tubes are used in hydrogen and ammonia reformers, ethylene and hydrocarbon cracking, power plant superheaters, heat-treatment furnaces, sulphuric and phosphoric acid plants, seawater-cooled heat exchangers and sour gas production. Matching products include Incoloy sheets and plates, Incoloy round bars, Incoloy flanges, Incoloy pipe fittings and Incoloy fasteners. Pipes and tubes in other materials are on the seamless pipes and tubes page.