What ASTM B443 Covers
ASTM B443 is the flat-product specification for UNS N06625, the alloy sold commercially as Inconel 625. It applies to hot-rolled and cold-rolled plate, sheet and strip, and it fixes the chemical composition, mechanical property minimums, permissible variations in thickness and the heat-treated condition in which the material is delivered. The ASME boiler-code equivalent is SB-443, used when the plate feeds a pressure part built to the ASME Code.
The standard matters because Inconel 625 is specified where chloride pitting, crevice attack, chloride stress-corrosion cracking and strong acids all have to be resisted at once, often at elevated temperature. Buying to B443 with a mill test certificate is how a fabricator proves the heat actually meets that chemistry and strength before it goes into a vessel, liner or weld overlay.
Inconel 625 Chemical Composition (UNS N06625)
The composition is built around a high nickel base with roughly 21.5% chromium for oxidation resistance and about 9% molybdenum with niobium for solid-solution strength and pitting resistance. The low carbon limit and the niobium plus tantalum addition are what keep the alloy stable through welding.
| Element | Symbol | Composition (weight %) |
|---|---|---|
| Nickel | Ni | 58.0 min |
| Chromium | Cr | 20.0–23.0 |
| Molybdenum | Mo | 8.0–10.0 |
| Niobium + Tantalum | Nb + Ta | 3.15–4.15 |
| Iron | Fe | 5.0 max |
| Carbon | C | 0.10 max |
| Manganese | Mn | 0.50 max |
| Silicon | Si | 0.50 max |
| Aluminium | Al | 0.40 max |
| Titanium | Ti | 0.40 max |
| Cobalt | Co | 1.0 max |
| Phosphorus | P | 0.015 max |
| Sulfur | S | 0.015 max |
Mechanical Properties
The property minimums depend on the delivered condition. The annealed condition is the general corrosion-service temper, while the solution-annealed condition is grain-coarsened for creep and rupture strength in high-temperature work.
| Property (annealed condition) | Minimum value |
|---|---|
| Tensile strength | 120 ksi (827 MPa) |
| Yield strength, 0.2% offset | 60 ksi (414 MPa) |
| Elongation in 2 in. | 30% |
Grade 1 and Grade 2 Conditions
ASTM B443 recognizes two tempers, and getting the condition right on the purchase order is as important as the grade itself.
| Condition | Heat treatment | Typical use |
|---|---|---|
| Grade 1 (annealed) | Annealed, finer grain | Aqueous corrosion and moderate-temperature service, best formability and short-term strength |
| Grade 2 (solution annealed) | Solution annealed, coarser grain | Elevated-temperature service where creep and stress-rupture strength govern |
A common ordering error is leaving the condition blank and receiving the wrong temper for the duty. If the part sees sustained high temperature, call out the solution-annealed condition so the heat is supplied grain-coarsened rather than fine-grained.
Equivalent Specifications and Designations
Inconel 625 carries one chemistry under several numbering systems. Matching the designations avoids receiving-inspection disputes when a drawing cites one system and the mill certificate another.
| System | Designation |
|---|---|
| UNS | N06625 |
| Werkstoff (W.Nr.) | 2.4856 |
| EN name | NiCr22Mo9Nb |
| ASTM (plate, sheet, strip) | B443 |
| ASME (boiler code) | SB-443 |
| Bar and rod | ASTM B446 |
Corrosion and High-Temperature Performance
The value of Inconel 625 is that it fights several mechanisms at the same time. The high molybdenum and niobium drive strong resistance to chloride pitting and crevice corrosion, the nickel base resists chloride stress-corrosion cracking that attacks austenitic stainless grades, and the chromium handles oxidizing conditions. That combination holds up in reducing and oxidizing acids, in seawater, and in hot process chlorides where 316L or even 904L reach their limits.
Because the alloy also keeps useful strength at red heat, B443 plate is used for aerospace components, flue-gas desulfurization liners, bellows, and weld-overlay cladding on carbon-steel vessels. For sour oil and gas service, confirm the required condition against NACE MR0175 / ISO 15156 on the order so the heat is supplied qualified. See our note on pitting corrosion and the wider nickel alloys explained primer for the mechanisms behind these choices.
Forms, Companion Standards and Grade Alternatives
B443 governs the flat product. A full Inconel 625 scope of supply pulls in companion specifications for the other forms, all available ex-stock with matching certification.
| Form | Specification |
|---|---|
| Plate, sheet, strip | ASTM B443 |
| Bar and rod | ASTM B446 |
| Forgings | ASTM B564 |
| Wrought buttweld fittings | ASTM B366 |
For the material itself, see Inconel 625 plate and Inconel 625 sheet, or the full Inconel 625 grade page. When the duty is sour or acidic rather than high-temperature, compare the choice in our Incoloy 825 vs Inconel 625 guide. Related nickel-alloy flat-product specifications include ASTM B575 for Hastelloy C-276 / C-22 and ASTM B409 for Incoloy 800 / 825. Typical end uses sit across oil and gas, chemical processing and pollution control.
Specifying and Ordering B443 Inconel 625
State four things on the purchase order: the specification (ASTM B443 or ASME SB-443), the condition (annealed Grade 1 or solution annealed Grade 2), the form and dimensions, and any supplementary testing such as NACE qualification or ultrasonic inspection. Every Nandini Steel order ships with an EN 10204 3.1 or 3.2 mill test certificate tying the plate back to its heat, so chemistry and mechanicals are traceable at receiving. Material is genuine mill product held in ready stock for immediate dispatch.
Frequently Asked Questions
What is ASTM B443?
What grade is ASTM B443?
What is the difference between ASTM B443 and ASME SB-443?
Is Inconel 625 better than 316L for seawater?
Does Nandini Steel supply B443 Inconel 625 from stock?
Request a Quote
Need B443 Inconel 625 plate, sheet or strip to a specific condition and size? Contact Nandini Steel for live pricing and stock through our contact page or WhatsApp +91 99202 09184, and send your specification for a same-day RFQ.