ASTM B443 UNS N06625 Nickel Alloy Plate

ASTM B443 UNS N06625 Nickel Alloy Plate combines high strength at both ends of the temperature range, excellent oxidation resistance, and corrosion resistance that spans seawater, acids, and chlorides, all without the precipitation-hardening heat treatment that other high-strength nickel alloys require. The alloy does its work in the solution-annealed condition, which is exactly why fabricators and operators trust it: the plate is as strong as it will ever be, straight from the mill, and it stays weldable and formable. 

Product Forms

Bar & Rod

Plate & Sheet

Coil & Strip

Pipe & Tube

Fitting: Flange, Tee, Elbow, Reducer etc.

Forging: Ring, Shaft, Circle, Block etc.

ASTM B168 Inconel 625 Sheets, Plates Specification

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The composition that makes it an all-rounder

Three elements do the heavy lifting. The chromium at 20-23% plus molybdenum at 8-10% give the plate its outstanding resistance to oxidizing media, chlorides and seawater - the corrosion record that made 625 the standard in marine, chemical and offshore service. The niobium plus tantalum at 3.15-4.15% is the quiet workhorse: it strengthens the solid-solution matrix and, in welding, locks up carbon so the weld metal keeps its strength and corrosion resistance without a heat treatment. That niobium addition is why 625 welds with matching filler and needs no post-weld aging.

Mechanical properties, hot-rolled plate (ASTM B443)

Note what the table does not say: no aging, no precipitation heat treatment, no condition requirement beyond solution annealing. Grade 1 (annealed) 625 plate delivers this strength as-delivered, and the strength actually increases toward cryogenic temperatures instead of falling - a signature of the nickel family that matters in LNG and low-temperature chemical service.

The service envelope: temperature and medium together

This breadth is the reason 625 is described as pre-qualified: it appears in aerospace, subsea, chemical, marine, nuclear and food applications without re-qualification, because the corrosion record and the fabrication record are both decades long.

Typical applications for 625 plate

• Offshore and marine - seawater systems, splash-zone cladding, subsea equipment
• Chemical process - reactor linings, piping spools, heat exchanger parts
• Aerospace and high-temperature - combustion and exhaust components, ducting
• Flue-gas desulfurization and pollution control
• Cryogenic equipment where notch toughness matters

Welding and fabrication

625 plate welds with matching filler from the 625 family (ERNiCrMo-3 per AWS A5.14) and, because the alloy is strengthened in solution rather than by precipitation, the weld does not need a post-weld heat treatment to restore strength - the niobium addition prevents the weld-metal strength loss that would otherwise occur. This is the practical advantage that makes 625 the default choice for complex fabricated equipment where post-weld heat treatment is difficult or impossible.

Sizes and delivery per ASTM B443

Ordering checklist

• Grade and standard: "Inconel 625 plate, UNS N06625, per ASTM B443, Grade 1 (annealed)"
• Dimensions: thickness x width x length, and quantity
• Edge condition: sheared, plasma-cut, or machined, with tolerances
• Service duty on the enquiry - temperature and medium, to confirm grade and thickness
• Certificate: EN 10204 3.1 with heat chemistry, tensile results and heat-treat record

Inconel 625 plate is the answer when the service is demanding but the failure mode is not yet clear - when seawater, high temperature, and acids could all appear in the same system. Its strength is as-delivered, its weld is as strong as the plate, and its service record spans five decades. That is what an all-rounder means in the nickel family.

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