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Alloy 31

  • Material

    Alloy 31, UNS N08031, W.Nr. 1.4562

  • Overview

    Alloy 31 is an iron-nickel-chromium-molybdenum alloy with the addition of nitrogen. The alloy closes the gap between high alloyed austenitic special stainless steels and nickel alloys. 

  • Character

    Alloy 31 is characterized by:

    Outstanding corrosion resistance in alkaline and acidic halide-containing media

    Excellent resistance to sulfuric acid, even in highly concentrated form

    Excellent resistance to corrosion and erosion in phosphoric acid media

    Outstanding resistance to surface corrosion and local corrosion in chlorine dioxide bleaching plants in paper production

    Excellent resistance in reducing and oxidizing media as well as in boiling azeotropic nitric acid

    Good workability and weldability

  • Application

    Typical application for Alloy 31 are:

    Components for flue gas desulfurization plants

    Plants for the production of phosphoric acid via the wet digestion process

    Pipes and heat exchangers for sulfuric acids contaminated with chlorides

    Pipes containing ocean water and brackish water, condensers and chillers

    Pickling plants for sulfuric acid as well as nitric-hydrofluoric acid

    Treatment of sulfuric acids from waste

    Evaporation and crystallization of salts

    Components for the cellulose and paper industry

    Digestion of ores, e.g. in HIPAL (high-pressure acid leach) plants for the digestion of laterite ores

    Mineral oil production and refineries

    Organic acids and ester synthesis

    Fine chemicals

    Strain-hardened transport and feed pipes as well as slicklines, wirelines and flowlines in the transport of oil and gas

  • Chemical Composition (wt% as per ASTM B622)








    Alloy 31














    Alloy 31






  • Mechanical Property

    Alloy 31 in the solution annealed condition as per ASTM B622


    Tensile strength

    ksi (MPa)

    Yield strength at

    0.2 offset ksi (MPa)

    Elongation in 2”

    % min.

    Reduction of area

    % min.


    ≥94 (650)

    ≥40 (276)


  • Corrosion Resistance

    Optimal corrosion resistance is only ensured if the material is used in a solution annealed, clean and metallic bright condition. The chemical composition of Alloy 31 is designed to enable the achievement of a high corrosion resistance in halide containing media. At the same time, the material has excellent resistance in pure and contaminated sulfuric acid over a broad range of concentrations and temperatures up to 80°C (176°F).


    The resistance to inter-crystalline corrosion (IC) was determined both according to ASTM G28, method A, and according to SEP 1877 II. Alloy 31 becomes sensitized only after prolonged exposure. The resistance to pitting was determined via potential measurements and through testing according to ASTM G48 under staged temperature increases and the use of the same samples.


    Alloy 31 is suitable only for applications in organic chemistry and for processes in which hydrochloric acid occurs only in low concentrations below 5% and this only at room temperature or slightly elevated temperatures. This is clearly shown by the ISO corrosion diagram in hydrochloric acid and by other investigations at room temperature as well as with acid concentrations in the range of 10% to 30%, which yielded erosive corrosion rates of up to 0.5 mm/year (0.02 in/year).

  • Available Process

    (1) Hot formed, annealed, descaled

    (2) Cold worked and bright annealed

    (3) Cold worked, bright annealed, polished (MP, EP, CP etc.)

  • Available Process

    (1) Hot formed, annealed, descaled

    (2) Cold worked and bright annealed

    (3) Cold worked, bright annealed, polished (MP, EP, CP etc.)

  • Common Tests

    Chemical composition






    Micro structure



    Intergranular Corrosion

    Surface condition

    Shape and dimension

    Positive Material Identification

  • Product Forms


    Size range

    Capillary tube

    OD 0.15 ~ 6.0 mm

    WT 0.015 ~ 1.5 mm

    Thin wall & Ultra thin wall seamless tube

    OD6.0 ~80.0 mm

    WT 0.05 ~4.5 mm

    Micro ID and heavy thick wall seamless tube

    OD3.0 ~50.0 mm

    ID 0.30 ~5.0 mm

    Precision conic seamless tube

    Bigger end: OD3.0 - 426.0mm

    Smaller end: OD2.5 - 346.0mm

    WT: 0.15 - 40.0mm

    HP /UHP BA+ tube

    EP tube

    OD 1.0 ~ 76 mm

    WT 0.10 ~ 10.0 mm

    Small caliber precision seamless tube

    OD6.0 ~89 mm

    WT 0.50 ~9.0 mm

    Profiled seamless tube

    Build to drawing

    Build to specification

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