What ASTM B446 Covers
ASTM B446 defines hot-worked and cold-worked round, square, hexagonal and flat bar, along with rod and forging stock, in the nickel-chromium-molybdenum alloy UNS N06625, commonly known as Inconel 625 or Alloy 625. The specification fixes the chemistry, the supply condition, the minimum mechanical properties and the dimensional tolerances that a mill must meet before a heat is accepted.
It is the long-product companion to the flat-product standard. Where plate, sheet and strip are ordered to ASTM B443, round bar and rod are ordered to ASTM B446. Forgings in the same alloy fall under ASTM B564, and wrought buttweld fittings under ASTM B366. Quoting the right form standard on the purchase order keeps the mill test certificate aligned with the part you actually receive.
Alloy 625 sits in the nickel-molybdenum-chromium family. If you are new to the behavior of these materials, our overview of nickel alloys explains why the high nickel base, chromium and molybdenum combine to resist both reducing and oxidizing environments.
Chemical Composition (UNS N06625)
ASTM B446 ties the bar grade to the UNS N06625 chemistry. The high nickel base with roughly 21 to 22 percent chromium, 9 percent molybdenum and a niobium addition gives Alloy 625 its combination of strength and broad corrosion resistance.
| Element | Composition (weight %) | Role |
|---|---|---|
| Nickel (Ni) | 58.0 min | Alloy base, general corrosion resistance |
| Chromium (Cr) | 20.0–23.0 | Oxidation and oxidizing-acid resistance |
| Molybdenum (Mo) | 8.0–10.0 | Pitting, crevice and reducing-acid resistance |
| Niobium + Tantalum (Nb+Ta) | 3.15–4.15 | Stabilization and solid-solution strengthening |
| Iron (Fe) | 5.0 max | Residual |
| Carbon (C) | 0.10 max | Controlled to limit carbide formation |
| Manganese (Mn) | 0.50 max | Residual |
| Silicon (Si) | 0.50 max | Residual |
The high molybdenum content is what carries the pitting and crevice resistance that lower-alloyed stainless grades cannot reach. For the background on how molybdenum and chromium set pitting behavior, see our note on PREN and pitting resistance.
Mechanical Properties and Conditions
ASTM B446 supplies Alloy 625 bar in more than one metallurgical condition, and the minimum mechanical properties depend on that condition. Annealed material offers higher strength from grain-boundary carbides, while solution-annealed material is softer and tougher for service above about 650 degrees C.
| Condition | Tensile strength, min | Yield strength (0.2%), min | Elongation, min |
|---|---|---|---|
| Annealed (Grade 1) | 827 MPa (120 ksi) | 414 MPa (60 ksi) | 30% |
| Solution annealed (Grade 2) | 690 MPa (100 ksi) | 276 MPa (40 ksi) | 30% |
Call out the intended condition on the order. For aqueous corrosion and high-strength structural duty the annealed grade is usual, while high-temperature creep service generally specifies the solution-annealed grade.
Equivalent and Related Standards
| Reference | Designation |
|---|---|
| Alloy / common name | Inconel 625, Alloy 625 |
| UNS number | N06625 |
| ASTM bar and rod | ASTM B446 |
| ASTM plate, sheet and strip | ASTM B443 |
| ASTM forgings | ASTM B564 |
| ASTM wrought fittings | ASTM B366 |
For cross-system equivalents across UNS, Werkstoff, JIS and EN, use the UNS, WNr and JIS cross-reference.
Typical Applications
Alloy 625 bar to ASTM B446 is specified where the part must survive both corrosive media and elevated temperature. Round bar is machined into shafts, valve stems, fasteners, pump and valve internals, and instrumentation components.
- Oil and gas: wellhead and subsea hardware, sour-service components and seawater-exposed parts.
- Petrochemical: reactor internals, bellows and high-temperature fasteners.
- Chemical processing: valve and pump parts handling mixed and reducing acids.
- Marine: propulsion and seawater-system shafting resistant to chloride pitting.
- Pollution control: scrubber and flue-gas hardware exposed to hot, acidic condensates.
Where you are weighing 625 against a nickel-iron-chromium alloy for sour or acid duty, our Incoloy 825 vs Inconel 625 comparison lays out the trade-offs.
Inconel 625 Bar, Rod and Other Forms from Stock
Nandini Steel supplies Inconel 625 as Inconel round bar to ASTM B446, backed by the broader round-bar range. The same alloy is held as Inconel 625 plate and Inconel 625 sheet, and the full Inconel 625 grade page covers properties and forms in one place.
Nandini Steel is an ISO 9001:2015-certified stockist and supplier established in 2003. All stock is held for immediate dispatch, and every order ships with an EN 10204 3.1 or 3.2 mill test certificate for full traceability. To date we have delivered 307-plus projects to 260-plus clients across 36-plus export countries.
Frequently Asked Questions
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Nandini Steel holds Inconel 625 bar and rod to ASTM B446 ex-stock for immediate dispatch. For sizes, conditions and live pricing, contact our team or message us on WhatsApp at +91 99202 09184 with your requirement.