Inconel – Grades, Products & Specifications
Inconel is the trade name for a family of nickel-chromium alloys that keep their strength and resist oxidation and corrosion at high temperatures, and stand up to many corrosive chemicals. Giriraj Impex supplies Inconel 600, 601, 625 and 718 as pipes, tubes, plates, sheets, round bars, wires, flanges, pipe fittings and fasteners, to the ASTM B specifications for each alloy.
We manufacture Inconel flanges, fittings, bars, wires and fasteners, and stock and supply Inconel pipes, tubes, plates and sheets from approved mills. Material is also supplied under its UNS number for buyers who specify the generic alloy.
Inconel grades
| Alloy | UNS | WNR | Key feature |
|---|---|---|---|
| Inconel 600 | N06600 | 2.4816 | Nickel-chromium-iron alloy for oxidation and chloride stress corrosion resistance |
| Inconel 601 | N06601 | 2.4851 | Aluminium addition for oxidation resistance at very high temperature |
| Inconel 625 | N06625 | 2.4856 | Molybdenum and niobium for strength, pitting and crevice corrosion resistance |
| Inconel 718 | N07718 | 2.4668 | Age-hardenable alloy for high strength in fasteners, shafts and components |
Inconel products and specifications
| Product | Inconel 600 | Inconel 625 |
|---|---|---|
| Seamless pipes and tubes | ASTM B167 | ASTM B444 |
| Welded pipes and tubes | ASTM B517, B516 | ASTM B705, B704 |
| Plates and sheets | ASTM B168 | ASTM B443 |
| Round bars and wires | ASTM B166 | ASTM B446 |
| Flanges and forgings | ASTM B564 | ASTM B564 |
| Pipe fittings | ASTM B366 | ASTM B366 |
| Fasteners | Machined from bar to the alloy specification | |
Inconel 601 is supplied to the same specifications as 600 (B166, B167, B168), and Inconel 718 bar and forgings to ASTM B637 and plate to B670. Detailed pages: Inconel 625 pipes and tubes and Inconel 625 round bars.
Where Inconel is used
Inconel 600 is used for furnace components, heat-treatment fixtures, chemical and food processing equipment and nuclear steam-generator tubing, where its high nickel content gives resistance to chloride stress corrosion cracking and to oxidation. Inconel 601 is chosen for radiant tubes, muffles and burner parts at the highest temperatures. Inconel 625 is the most versatile grade: it is used for seawater and offshore piping, flare stacks, chemical process equipment, flue gas desulphurisation, and as a weld overlay and cladding alloy, because it combines strength with strong resistance to pitting and crevice corrosion. Inconel 718 is age hardened for high-strength parts such as bolting, shafts, valve stems and oilfield components.
In aerospace and power generation, nickel-chromium alloys of this family are also used for exhaust ducting, combustion hardware, springs and fasteners that must keep their strength when hot. For industrial buyers, the practical message is that the alloy is chosen for temperature and corrosion together, and the product specification and heat-treatment condition must match the service.
Working with Inconel
Nickel alloys work-harden quickly, so machining uses rigid set-ups, sharp tools and steady feeds. Welding uses matching or over-alloyed filler metals and clean joints, as sulphur and lead contamination can cause cracking. Inconel 625 is normally supplied annealed; Inconel 718 is supplied solution annealed and can be age hardened after machining. Please state the heat-treatment condition on the order.
Inconel parts that will see high temperature should be designed with its thermal expansion in mind, which is lower than that of austenitic stainless steels but higher than carbon steel. Where Inconel is joined to other alloys in hot service, the difference in expansion and the choice of filler metal are part of the design review.
Inconel in oil, gas and chemical plants
In oil and gas, Inconel 625 is used for seawater-cooled heat exchangers, flowlines and risers, sour-service components and as cladding inside carbon steel pipe and vessels, because it combines strength with resistance to chloride pitting and sulphide stress cracking. In chemical plants, alloy 600 handles hot caustic solutions and high-temperature chlorination, while 625 resists phosphoric, sulphuric and mixed acids. In power and heat treatment, alloys 600 and 601 are used for furnace muffles, retorts, radiant tubes and thermocouple sheaths that must survive repeated heating and cooling.
When ordering, state the alloy and UNS number, the ASTM product specification, the heat-treatment condition (annealed, solution annealed or age hardened), the dimensions and quantity, and any NACE MR0175 / ISO 15156 or third-party inspection requirement.
Documents and inspection
Inconel material is supplied with mill test certificates (MTC) showing heat number, composition, mechanical properties and heat treatment. Third-party inspection is available on request, and material can be supplied to NACE MR0175 / ISO 15156 on request. For other nickel alloys see Incoloy, Monel and Hastelloy, or browse all materials.
Frequently Asked Questions
Inconel is a trade name for a family of nickel-chromium based alloys, such as 600, 625 and 718. They keep their strength at high temperature and resist oxidation and many corrosive environments. Generic material is specified by UNS number, for example N06625 for alloy 625.
Inconel 600 is a nickel-chromium-iron alloy used mainly for heat and oxidation resistance. Inconel 625 adds molybdenum and niobium, giving higher strength and much better resistance to pitting and crevice corrosion, so it is used in seawater and chemical service.
ASTM B444 covers seamless Inconel 625 (UNS N06625) pipe and tube. Welded 625 pipe is covered by ASTM B705 and welded tube by ASTM B704.
Inconel 600 and 625 are essentially non-magnetic at room temperature. Their high nickel content gives an austenitic structure similar to 300 series stainless steels.
Inconel 718 is an age-hardenable alloy with very high strength. It is used for high-strength bolting, shafts, springs, valve stems and oil and gas components, and is supplied to ASTM B637 for bar and forgings.
Yes. Inconel alloys are regularly welded to stainless and carbon steels using nickel-based filler metals selected for the combination. The welding procedure should be qualified for the dissimilar joint.
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Inconel®, Incoloy® and Monel® are trademarks of Special Metals Corporation; Hastelloy® of Haynes International.