Specifications

Chemical composition and mechanical properties

The table shows the ASTM A105 requirements. Actual values for each heat are given on the mill test certificate.

Limits on combined Cu, Ni, Cr, Mo and V, and the manganese allowance for lower carbon, are as given in the standard.

Elongation requirements depend on the test specimen, as given in the standard.

ASTM A105 limits hardness to a maximum of 187 HB, which keeps the forging ductile and suitable for welding to carbon steel pipe without preheat in most wall thicknesses. The low carbon equivalent is one reason A105 is used so widely for weld neck and slip-on flanges.

Pressure ratings of A105 flanges

ASTM A105 is in material group 1.1 of ASME B16.5. The table shows the working pressure of each class at −29 °C to 38 °C. Ratings fall as the temperature rises, so the B16.5 table for group 1.1 at the design temperature should always be used for design.

Class 150 and 300 cover most water, utility and low-pressure hydrocarbon lines; Class 600 and above are used for high-pressure process, steam, gas and well-fluid lines, usually with weld neck flanges and, from Class 900 up, often with RTJ facings.

How we manufacture A105 flanges

A105 flanges are made from forged carbon steel billets or bars. The material is forged close to the final shape, heat treated where the standard or the order requires it, and then machined to the dimensions of ASME B16.5 or the specified standard. Machining covers the bore, facing, flange thickness, hub, bolt holes and the face finish. Flanges are then marked, inspected and protected against rust before dispatch.

ASTM A105 requires heat treatment for certain parts, including flanges above Class 300. Many purchasers specify normalised A105 for all classes, as normalising refines the grain and gives more uniform properties; such flanges are often marked A105N. Please state any heat-treatment requirement in the enquiry.

A105 for sour service and low temperatures

For wet sour service containing hydrogen sulphide, A105 flanges can be supplied to NACE MR0175 / ISO 15156 on request, with controlled hardness and the testing the standard requires; please mention this in the enquiry. A105 has no impact test requirement, so it is not used where the minimum design temperature is below −29 °C. For low-temperature service, ASTM A350 LF2 flanges, impact tested at −46 °C for Class 1, are used instead – see carbon steel flanges for the full material range.

Marking, inspection and ordering

Each A105 flange is marked with the manufacturer's identification, ASTM A105, size, class, facing, bore or schedule where applicable, and heat number, in line with ASME B16.5 and MSS SP-25. Inspection covers dimensions, face finish, bolt holes and marking, and the mill test certificate reports chemistry and mechanical tests for the heat.

Please give the flange type, size, class, facing and face finish, bore or pipe schedule for weld neck and socket weld flanges, coating, quantity, and any NACE MR0175 / ISO 15156, impact test, ultrasonic test or third-party inspection requirement.

Applications and matching products

A105 flanges are used in hydrocarbon and process lines, steam and condensate, boiler feed water, cooling water, firewater, compressed air and instrument air systems in refineries, petrochemical and fertiliser plants, power stations, oil and gas facilities and general industry. They are paired with A106 Grade B and API 5L pipe, A234 WPB butt-weld fittings, A105 forged fittings and B7/2H stud bolts. See flanges for every flange type and material, and the carbon steel page for guidance on carbon steel grades.