Nickel alloy forgings / UNS N06693

UNS N06693 Forgings (Inconel® 693)

Open-die forged rings, flanges, round bars, discs, shafts, sleeves and tube sheets in UNS N06693, the nickel-chromium-aluminium alloy used where metal dusting attacks conventional grades.

UNS number

N06693

Trade name

Inconel® 693

Alloy type

Ni-Cr-Fe-Al

Density

7.77 g/cm³

Forging standard

ASTM B564

Condition

Solution annealed

Weight range

10 to 15,000 kg

Certificate

EN 10204 3.1 / 3.2

What UNS N06693 is, and when to specify it

Alloy 693 was developed by Special Metals as a successor to alloy 690 for one problem: metal dusting. In gas streams rich in carbon monoxide and hydrogen, such as syngas plants, steam methane reformers, direct reduction iron units, ammonia plants and methanol plants, carbon activity can exceed unity and attack the metal. The metal breaks down into a dust of metal particles, carbides and coke. Failures happen in months rather than years, and they are usually localised, so one wrong component can stop a train.

High chromium on its own is not enough. N06693 carries a deliberate addition of 2.5 to 4.0% aluminium, which forms an alumina-rich sublayer under the chromia scale. That sublayer is much less permeable to carbon. The alloy also holds good oxidation and sulfidation resistance in oxidising and reducing sulfur-bearing atmospheres, and it has performed well against oxide-rich media such as glass frit and fluxing compounds at temperatures up to about 1100 °C.

The cost of that aluminium is workability. Alloy 693 is harder to hot work and harder to weld than alloy 600 or alloy 690. Forging temperature, reduction schedule and die practice matter more than they do for a plain Ni-Cr grade, which is why buyers usually source it as a finished forging rather than as billet for machining.

Chemical composition of UNS N06693

Limits published in supplier datasheets for the wrought alloy. Heat specific analysis is reported on the mill certificate supplied with every order.

Physical and mechanical properties

Physical properties at room temperature

Mechanical properties

Typical published values for annealed plate, given for orientation. Forging properties depend on section size, reduction ratio, test location and heat treatment condition. The values that govern acceptance are those on the mill test certificate for the heat supplied. Published elastic modulus figures for alloy 693 differ between sources, so ask for confirmed data before using it in a design calculation.

Forged products and size range

Every item below is produced to your drawing or specification. These are open-die forgings and seamless rolled rings, so there is no die cost and single prototype pieces are accepted.

Shop equipment: 1 t, 3 t, 6 t and 9 t forging hammers, a 4500 t hydraulic press, and 3 m and 6 m seamless ring rolling mills. Sizes achievable in N06693 depend on ingot availability. Send the drawing and we will confirm before quoting.

Production route

1. MeltingVIM plus ESR for nickel-base superalloy stock. EAF plus VOD plus ESR route where the ingot source allows.
2. Open-die forgingHammers to 9 t and a 4500 t press. Controlled heating, reduction ratio and finishing temperature to develop a sound wrought structure.
3. Ring rolling3 m and 6 m mills for seamless and contoured rolled rings with no weld seam.
4. Heat treatmentSolution annealing at 1010 to 1066 °C, soak by section thickness, rapid air cool or water quench.
5. MachiningRough or finish machined to your drawing, including bores, faces, grooves and drilled patterns.
6. TestingChemistry, tensile, hardness, ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388. PMI, PT, impact and IGC on request.
7. CertificationEN 10204 3.1, or 3.2 witnessed by TUV, BV, SGS, Lloyd's or your own inspector.
8. Packing and despatchSeaworthy wooden cases or steel pallets, marked by heat number, ex Shanghai or Zhangjiagang.

Standards, testing and certification

N06693 forgings are normally ordered against ASTM B564, the specification for nickel alloy forgings, with chemistry to the UNS limits also used in ASTM B166 for bar and rod. Related product form specifications are ASTM B168 for plate, sheet and strip, and ASTM B167 for pipe and tube. We also work to customer specifications, client technical manuals, and NACE MR0175 / ISO 15156 requirements where sour service applies.

Ultrasonic acceptance is normally agreed to EN 10228-3, SEP 1921 or ASTM A388 with a stated quality class. Certificates are issued to EN 10204 3.1 as standard, or 3.2 with third party witness. Tests available on request include positive material identification, Charpy impact testing at low temperature, grain size determination, intergranular corrosion testing, dye penetrant inspection and hardness surveys.

Where UNS N06693 forgings are used

Syngas, hydrogen and petrochemical plant

Steam methane reformer outlet components, syngas coolers and transfer line hardware, direct reduced iron process equipment, ammonia and methanol synthesis loops. Anywhere carbon activity is high enough to cause metal dusting. Typical parts: forged nozzles, tube sheets, flanges, rings and thick wall hollow sections.

Refining and chemical processing

Reactor internals, columns and towers, preheaters, process modules, digesters and evaporators exposed to carburising or sulfidising gas. Typical parts: forged rings, shafts, sleeves, discs and tube sheets.

Heat treatment and thermal processing

Furnace fixtures, burner nozzles, radiant tube components and retorts operating in reducing atmospheres. Also waste to energy and biomass incinerator hardware exposed to chloride and sulfur species.

Valves, pumps and rotating equipment

Forged valve bodies, seat rings, stems, blocks and bonnets for ball, gate, globe, check and plug valves in high temperature corrosive duty. Pump and agitator shafts, spindles, gears and bushings for power transmission and compressor service.

UNS N06693 compared with alloys 690, 601 and 602 CA

Where the failure mode is metal dusting or high temperature carburisation, alloy 693 is the grade to specify. For aqueous corrosion and oxidising acids, alloy 690 is usually cheaper and adequate. For long term creep above 1000 °C, look at 602 CA or alloy 617. We forge all of them.

About the manufacturer

Frequently asked questions about UNS N06693

Data sources and reference

Composition and physical property limits on this page follow published wrought alloy datasheets for Inconel® 693 / UNS N06693, cross-checked against more than one source. Manufacturing capability, testing scope and certification statements describe the facilities of Jiangyin Jiangnan Metal Co., Ltd. None of it replaces the mill test certificate issued with a specific heat, or the applicable purchase specification.