ASTM-Standard Inconel 625 Nickel Alloy Round Bars in Custom Sizes
ASTM-Standard Inconel 625 Nickel Alloy Round Bars are
high-performance materials designed for extreme service conditions,
offering an exceptional balance of strength, corrosion resistance,
and manufacturability. These round bars are produced according to
strict international standards, primarily ASTM B446, ensuring
consistency and reliability for critical applications across
aerospace, marine, and chemical processing industries .
This article provides a detailed overview of these custom-sized
round bars, covering their chemical composition, mechanical
properties, standards, key characteristics, applications, and
packaging.
1 Chemical Composition
The outstanding properties of Inconel 625 are derived from its
precise nickel-chromium base enhanced with solid-solution
strengthening elements like molybdenum and niobium. The following
table outlines its typical chemical composition as per standard
specifications .
Element | Content (%) | Element | Content (%) |
|---|
Nickel (Ni) | Balance (approx. 58% min) | Iron (Fe) | ≤ 5.0 |
Chromium (Cr) | 20.0 - 23.0 | Aluminum (Al) | ≤ 0.40 |
Molybdenum (Mo) | 8.0 - 10.0 | Titanium (Ti) | ≤ 0.40 |
Niobium (Nb) | 3.15 - 4.15 | Carbon (C) | ≤ 0.10 |
Cobalt (Co) | ≤ 1.0 | Manganese (Mn) | ≤ 0.50 |
Silicon (Si) | ≤ 0.50 | Phosphorus (P) | ≤ 0.015 |
Copper (Cu) | ≤ 0.07 | Sulfur (S) | ≤ 0.015 |
The combination of chromium provides excellent resistance to
oxidation and corrosion, while molybdenum and niobium confer
strength and resistance to pitting and crevice corrosion,
particularly in chloride-ion environments . The low carbon content
enhances its weldability by minimizing carbide precipitation .
2 Mechanical Properties
Inconel 625 round bars are typically supplied in the annealed or
solution-treated condition, offering a superb combination of high
strength and good ductility. The mechanical properties meet or
exceed the minimum requirements of standards like ASTM B446 .
The table below presents typical mechanical properties at room
temperature for solution-treated bars 110.
Property | Typical Value | Remarks |
|---|
Tensile Strength | ≥ 830 MPa (120 ksi) | May increase significantly with cold work . |
Yield Strength (0.2% Offset) | ≥ 415 MPa (60 ksi) |
|
Elongation (in 50 mm) | ≥ 30% | Indicates good ductility |
Hardness (Brinell) | 150 - 220 HB |
|
A key advantage of Inconel 625 is that its high strength is
achieved through solid-solution strengthening by molybdenum and
niobium, meaning it does not require precipitation hardening
treatments . This makes it particularly suitable for applications
involving welding, as it retains its properties in the as-welded
condition without post-weld heat treatment for stress relief in
many cases .
3 Applicable Standards
ASTM-standard Inconel 625 round bars are governed by specific
specifications that ensure material quality and consistency.
Primary Standard for Bars: ASTM B446 / ASME SB-446: This standard
covers the requirements for nickel-chromium-molybdenum-columbium
(niobium) alloy (UNS N06625) rods and bars .
Other Relevant Standards:
These standards strictly define the chemical composition limits,
heat treatment processes (typically solution annealing at
1090-1200°C followed by rapid cooling ), and minimum mechanical
properties .
4 Key Characteristics and Advantages
Inconel 625 round bars are chosen for demanding applications due to
their unique set of properties :
Excellent Corrosion Resistance: They exhibit outstanding resistance
to a wide range of severe corrosive environments, including
oxidation, reduction, pitting, and crevice corrosion. They are
highly resistant to chloride-induced stress corrosion cracking.
High-Temperature Strength: The alloy retains a significant portion
of its strength at elevated temperatures, making it suitable for
service from cryogenic temperatures up to about 980°C (1800°F) .
Outstanding Fabricability: These round bars possess good
machinability and can be welded readily using common techniques
like TIG, MIG, and plasma arc welding without post-weld heat
treatment cracking susceptibility .
High Strength and Toughness: The solid-solution strengthening
provides high tensile and fatigue strength, along with excellent
toughness at both cryogenic and elevated temperatures.
5 Common Applications
Custom-sized Inconel 625 round bars are machined into critical
components for various industries :
Aerospace Industry: Engine components, thrust reversers, ducting
systems, and rocket motor cases.
Marine and Offshore Engineering: Propeller blades, submarine parts,
mooring cables, and pump shafts for seawater handling due to
superior resistance to seawater corrosion.
Chemical Processing Industry: Agitators, heat exchanger tubes,
reaction vessels, and piping systems handling acidic chlorides and
other aggressive chemicals.
Pollution Control: Components in flue gas desulfurization systems,
such as absorber towers, dampers, and fan blades.
Nuclear Industry: Core components and control rod mechanisms due to
their high-temperature strength and corrosion resistance.
6 Packaging Options
To ensure the material arrives in perfect condition, especially for
high-value alloys like Inconel 625, suppliers typically offer
robust packaging solutions. While specifics can vary, common
practices include 58:
Individual Protection: Each round bar is often coated with
anti-corrosive oil and wrapped individually.
Secured Bundling: Bars are neatly bundled using steel straps to
prevent movement during transit.
Marking and Labeling: Clear markings indicating the material grade,
heat number, size, and other traceability information are
essential.
External Packaging: Bundles are typically packed in wooden crates
or cases for maximum protection during shipping and handling.
7 Conclusion
In summary, ASTM-standard Inconel 625 round bars in custom sizes
are a premier choice for engineers dealing with extreme
environments. Their robust chemical composition, governed by
standards like ASTM B446, delivers a reliable combination of high
strength, exceptional corrosion resistance, and excellent
fabricability. Whether for aerospace, marine, or chemical
processing applications, these round bars offer the performance and
reliability needed for critical components, backed by professional
packaging that ensures they arrive on-site ready for machining and
installation.
