Alloy 24 Forgings UNS S34565 · EN 1.4565 · ASTM A182 F49

The same material reaches us under several names. We accept enquiries against any of the following.

Limits below are the requirements of ASTM A182 grade F49. Heats are melted by AOD refining or vacuum induction melting, with vacuum arc or electroslag remelting where the order calls for it.

The manganese level is deliberate rather than incidental. Manganese raises nitrogen solubility in the melt, which is the only practical way to hold 0.4 to 0.6 % nitrogen in solid solution. Take the manganese out and the nitrogen comes out with it, along with the strength and pitting resistance that justify the grade.

Tensile min

795 MPa

Yield min

415 MPa

Elongation min

35 %

Red. of area min

40 %

Hardness

200 HB

PREN

47

Alloy 24 gets specified at the point where 316L, 317LMN and 904L have run out of margin against chlorides.

Published mill data credits the grade with resistance to intergranular corrosion, very high resistance to localised attack in the form of pitting and crevice corrosion, and good resistance to stress corrosion cracking in seawater and comparable media. It is approved under VdTUV Werkstoffblatt 509 for pressure applications from −196 °C to +400 °C. In a fair number of duties it substitutes for duplex grades, Alloy 31 or solid nickel alloys at lower cost.

One limit worth stating plainly: Alloy 24 has no specified copper addition. For dedicated hot sulfuric acid service the conventional choices are copper-bearing grades such as Alloy 20 (UNS N08020) or 904L. We forge all three, so tell us the medium, concentration and temperature and we will say which one fits rather than simply quoting what you asked for.

This grade work-hardens hard and has a narrow hot-working window, so process control matters more than it does on a 304 or 316 forging.

Our route is hot work between approximately 1150 °C and 950 °C with air cooling, then solution annealing between 1120 °C and 1170 °C (2050 to 2140 °F) followed by water quenching or equally rapid cooling by other means. The quench is not a formality. Cool slowly through the intermediate range and sigma and other intermetallic phases precipitate at the grain boundaries, taking the toughness and the pitting resistance with them.

Testing and certification

Ultrasonic examination follows EN 10228-4, the part of the EN 10228 series written for austenitic and austenitic-ferritic stainless forgings. EN 10228-3 covers ferritic and martensitic steels and is not the right document for this material, though it is frequently quoted in error. We also test to ASTM A388 or SEP 1921 on request. Certificates are issued to EN 10204 type 3.1, or type 3.2 endorsed by an independent body such as TUV, SGS, BV or Lloyd's Register.

Everything here is made to drawing or specification, as-forged, rough machined or finish machined.

Alloy 24 turns up wherever chloride content, acid concentration or both rule out the standard austenitics.

In power generation and marine service it goes into flue gas desulphurisation plant on land-based stations and large sea-going vessels, seawater piping systems, desalination plant, seawater ballast gate valves on tankers and seawater pumps. In chemical, petrochemical and oil work it appears as process piping, mixing tanks, reactor vessels, bubble caps, acid cleaning and pickling equipment, crude oil transfer hardware, wellhead and Christmas-tree components, and dredging transport systems in environmental technology. Pulp and paper, food and pharmaceutical plants use it for bleaching equipment, heat exchangers, crystallisers and processing lines handling pharmaceuticals, plastics, synthetic rubber and heavy organic chemicals. It also shows up in research hardware such as high-pressure deep-sea samplers, incubation chambers and underwater manipulator arms.