416 Annealed Stainless Round Bar properties at a glance
Values labeled typical are orientation- and section-dependent references, not design allowables. Use the current governing specification and the supplied mill certificate for acceptance.
| Property | Reference value | How to use it |
|---|---|---|
| Density | 0.280 lb/in³ (7.75 g/cm³) | Nominal value used by the NOX weight calculator |
| Structure | Martensitic stainless | Magnetic and hardenable by heat treatment |
| Supply condition | Annealed | Confirm hardness and condition on the mill cert |
| Machining behavior | Free-machining, short-chip behavior | Sulfur additions improve cutting performance |
| Corrosion behavior | Lower than 304 and 316 | Best in mild environments with appropriate surface care |
History of 416 (UNS S41600)
Martensitic chromium stainless traces to the first commercial stainless work of the 1910s, including alloys developed for cutlery and gun-barrel applications. These steels could be hardened and tempered, unlike austenitic 304 and 316. As automatic machining expanded, producers modified martensitic chemistry with sulfur to break chips and reduce cutting forces.
Type 416 became the familiar free-machining member of that family. Its success comes from a conscious compromise: sulfide inclusions make bar productive on lathes and screw machines, but interrupt the matrix in ways that reduce corrosion resistance, forming performance, weldability, and toughness. Annealed bar is supplied as a machinable starting point and can be heat treated when the drawing requires higher hardness.
- 1910s
Martensitic stainless is commercialized
Chromium steels establish a hardenable stainless family for cutlery and mechanical applications.
- Machine-age development
Sulfur improves chip control
Free-machining modifications support faster production of turned stainless parts.
- Today
416 remains a productivity-led choice
It is used where machining rate matters and the environment does not demand 304- or 316-level corrosion resistance.
Choose 416 for production machining
416 is attractive for turned parts because it breaks chips, reduces cutting load, and supports productive surface finishes. It fits fasteners, shafts, fittings, valve parts, and screw-machine components used in relatively mild environments. It is not the correct default merely because a part is stainless and round.
Compare corrosion, toughness, forming, and joining requirements first. If the component sees marine chlorides, hygienic chemicals, severe impact, or structural welding, 304, 316, 17-4, or another grade may be a better match even if machining takes longer.
Use the free-machining advantage responsibly
Annealed 416 is far easier to turn than austenitic stainless and is well suited to automated work. Stable tooling, appropriate speed, and chip control can produce excellent finishes. Sulfide stringers create directional behavior, so highly loaded transverse features or impact-sensitive parts deserve special attention.
The alloy can be hardened and tempered after machining, but heat treatment changes dimensions and properties. Plan finish stock and straightening, use the approved cycle, and preserve heat identity through the outside processor. Do not quote a final hardness from an annealed raw-bar certificate.
Confirm the free-machining bar specification
Specify 416 or UNS S41600, annealed condition, ASTM A582 when appropriate, diameter, cut length, finish or tolerance, and quantity. If the finished part will be hardened, add its required heat-treatment and hardness on the manufacturing drawing rather than assuming the raw-bar supplier will infer it.
Review the mill cert for chemistry, sulfur range, condition, hardness or mechanical results, specification, and heat number. Keep the grade distinct from 410 and from austenitic bars; a simple spark, magnet, or appearance check is not adequate alloy verification.
Specifications and purchase callouts
The controlling drawing decides which specification applies. A similar alloy name or typical-property table does not demonstrate compliance.
- ASTM A582 for free-machining stainless bar
- SAE AMS 5610 for aerospace bars, wire, and forgings
- UNS S41600 grade designation
Frequently asked questions
Why is 416 stainless easy to machine?
Its sulfur modification forms inclusions that help chips break and reduce cutting forces. That improves productivity and surface finish, especially in turning and screw-machine work, but it also creates tradeoffs in corrosion resistance, weldability, and toughness.
Is 416 as corrosion resistant as 304 or 316?
No. 416 is selected primarily for machinability and hardenability in relatively mild environments. 304 provides better general corrosion resistance, and 316 is usually preferred when chloride pitting is a concern.
Can annealed 416 be hardened after machining?
Yes, 416 is martensitic and can be hardened and tempered using an approved process. Heat treatment can change dimensions and straightness, so the process plan should include finish stock, verification, and the final hardness required by the drawing.
Which specification covers 416 round bar?
ASTM A582 is the common commercial specification for free-machining stainless bar. Aerospace orders may require SAE AMS 5610. State the exact specification and revision, UNS S41600 grade, condition, diameter, finish, and certification requirements on the purchase order.
Primary references
Technical standards change. These sources support the history and reference discussion; obtain the current specification revision for design or acceptance work.
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