416 Stainless Steel
Also: AISI 416, UNS S41600, 1.4005, X12CrS13, SUS416, free-machining 410, 416R (barrel grade), 416 Se (S41623)
416 is the free-machining martensitic stainless: the easiest stainless to machine at about 85% of B1112, hardenable to about 40 HRC. Bar only; do not weld it.
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At a glance
| Density | 7.75 g/cm³ (0.28 lb/in³) |
|---|---|
| Tensile strength | Annealed 515-550 MPa (75-80 ksi); hardened and tempered at 205 °C (400 °F) about 1310 MPa (190 ksi) |
| Yield strength | Annealed 275-310 MPa (40-45 ksi); hardened and tempered at 205 °C (400 °F) about 1000 MPa (145 ksi) |
| Hardness | Annealed 155-190 HB (about 82-90 HRB); hardened and tempered low 38-42 HRC; Condition T bar about 26-32 HRC |
| Elongation | Annealed 25-30%; hardened and tempered low about 12-15% |
| Modulus of elasticity | 200 GPa (29 Msi) |
| Thermal | Melts at 1480-1530 °C (2700-2790 °F); thermal conductivity ~25 W/m·K; expansion ~9.9 um/m·K; scales above about 700 °C (1300 °F) |
| Composition | Fe, 12-14% Cr, 0.15% min S, up to 0.15% C, up to 1.25% Mn, up to 1% Si, up to 0.6% Mo |
Typical values, First figure annealed (Condition A) bar; second figure hardened from 980 °C (1800 °F), oil quenched and tempered at 205 °C (400 °F). Confirm against the mill certificate and the purchase spec.
- MachinabilityExcellent
- About 85% of B1112, the highest of any stainless: short chips, low tool pressure, fine finishes. Pre-hardened bar at 26-32 HRC still machines well with coated carbide. Chips are fine and sharp; keep coolant on them.
- WeldabilityPoor
- Sulfur causes hot cracking and the martensitic heat-affected zone adds cold cracking on top. Avoid. If a tack is unavoidable, preheat, use 309L or 312 filler and expect a weak, corrosion-prone joint. Weld 410 instead.
- FormabilityPoor
- Sulfide stringers tear on bending and heading; knurling and light staking are the limit. No sheet is stocked. Form 410 and machine 416.
- Corrosion resistancePoor
- The lowest of the common stainless grades: fine indoors and in dry or lightly humid air, marginal in fresh water, rusts in chlorides and marine air. Harden, temper low, polish and passivate to get the most from it; oil or plate parts in harsher service.
416 is 410 with at least 0.15% sulfur. The manganese sulfides break the chip and lubricate the cut, so it machines at roughly 85% of the B1112 benchmark, faster than 303 and far faster than 304 or 410. It hardens exactly like 410, oil quenched from about 980 °C (1800 °F) and tempered, to about 1310 MPa (190 ksi) and 38-42 HRC. It is magnetic in every condition and is sold almost only as bar, much of it pre-hardened.
It is the choice for turned parts that need to be hard, magnetic or both while resisting mild corrosion: pump and valve shafts, gears, nuts and studs, solenoid cores and pole pieces, firearm barrels and receivers (the barrel-quality 416R variant), gauges and fixture pins. Screw-machine and Swiss shops run it for volume stainless hardware when 303 is not hard enough.
The sulfur costs it everywhere else. Corrosion resistance is the lowest of the common stainless grades (the sulfides are pit sites) and it needs the hardened, polished, passivated state to look like stainless at all. It hot-cracks when welded and tears when cold formed. Tempering in the 425-540 °C (800-1000 °F) band should be avoided, as for 410, and impact toughness in the hardened state is modest.
Heat treatment
Same cycles as 410. Anneal at 815-900 °C (1500-1650 °F) with a slow cool. Harden from 925-1010 °C (1700-1850 °F) with an oil quench or air cool, then temper: 205-370 °C (400-700 °F) for 38-42 HRC and the best corrosion resistance, or 595-705 °C (1100-1300 °F) for 24-30 HRC with better toughness. Avoid tempering at 425-540 °C (800-1000 °F). Much 416 is sold pre-hardened (Condition T, about 26-32 HRC, or Condition H, about 35-42 HRC per ASTM A582) so parts can be machined and used without a heat-treat cycle.
Tempers and conditions
- Annealed (Condition A)
- Condition T (intermediate temper, about 26-32 HRC)
- Condition H (hard temper, about 35-42 HRC)
- Hardened and tempered by the shop to a stated HRC
Stock forms
- Round, hex and square bar (the main form)
- Precision ground shafting
- Pre-hardened bar (Condition T and H)
- Wire
- Forgings (limited)
Relative cost
Tier 2 of 5. About the same as 410 and 10-25% under 304 per pound; the fast machining makes a 416 part the cheapest hardenable stainless part there is. Pre-hardened bar carries a small premium that is usually less than a heat-treat lot charge.
Typical applications
- Pump, valve and gear shafts
- Screw-machine nuts, studs and fittings
- Solenoid cores, pole pieces and magnetic components
- Firearm barrels, receivers and bolts (416R)
- Gears, pinions and worms
- Fixture pins, gauges and locating hardware
Process compatibility
How 416 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | ExcellentExcellent | The easiest stainless to cut; the default hardenable stainless for turned and milled parts in quantity. |
| Screw Machining | ExcellentExcellent | Multi-spindle and cam machines run 416 at near free-cutting steel speeds; pre-hardened bar skips the heat treat. |
| Swiss Machining | ExcellentExcellent | Precision ground 416 bar makes small shafts, cores and pins with fine finishes and short chips. |
| CNC Turning | ExcellentExcellent | Shafts and barrels turn and drill deep cleanly; Condition T bar is the usual stock for shafts. |
| Heat Treating | ExcellentExcellent | Oil quench from 980 °C (1800 °F) and temper to a stated HRC; or buy Condition T or H bar and skip it. Avoid the 425-540 °C temper band. |
| Induction Hardening | GoodGood | Shafts and journals surface-harden well for wear; specify pattern and case depth. |
| CNC Grinding | GoodGood | Hardened shafts and pins grind to tight size and finish; standard practice for precision pins. |
| Passivation | FairFair | Passivates, but a plain nitric bath can etch it grey; specify ASTM A967 citric or nitric with sodium dichromate and name the alloy on the order. |
| Black Oxide | FairFair | MIL-DTL-13924 Class 3 blackens hardened 416 for firearm and fixture parts; cosmetic, with some rust protection under oil. |
| Nickel Plating | FairFair | Electroless nickel gives 416 the corrosion resistance it lacks; the sulfides need a good activation, and hardened parts want a hydrogen bake. |
| Welding | Not recommendedNot recommended | Hot cracking from the sulfur plus air-hardening of the heat-affected zone; make welded members from 410 or 304L and join 416 mechanically. Can 416 stainless be welded? |
| Electropolishing | PoorPoor | Sulfide stringers pull out and leave a streaky, pitted surface; polish mechanically instead. |
| Press Brake Forming | Not recommendedNot recommended | No sheet, and the sulfides crack on the outside of any bend. |
Compare 416
Design and sourcing tips
- Specify "416 per ASTM A582" and the condition: "Condition A, harden and temper to 38-42 HRC after machining" or "Condition T pre-hardened" when the part is used as machined.
- Never weld it; if the assembly must be welded, make that member 410 or 304L and fasten or press the 416 part in.
- Call passivation per ASTM A967 by the citric method (or nitric with dichromate) and name the alloy so the shop does not flash-attack it.
- Keep it indoors or oiled: for anything outdoors or near chlorides, 416 is the wrong grade, and electroless nickel is the usual rescue.
- For magnetic circuits (solenoids, pole pieces) specify the annealed condition unless hardness is needed; annealed 416 has the higher permeability.
- Ask for barrel-quality 416R and the mill cert when the part is a firearm barrel; ordinary 416 has more sulfide stringers and can pit under the finish.
Frequently asked questions
- Is 416 stainless steel magnetic?
- Yes, in every condition. It is a 12-14% chromium martensitic stainless, so it is strongly magnetic, which is why it is used for solenoid cores and pole pieces. Annealed 416 has the higher permeability; hardened 416 is still magnetic but harder to magnetize.
- Can 416 stainless be welded?
- Not in practice. The sulfur that makes it machine causes hot cracking, and the heat-affected zone air-hardens and can cold crack as well. Shops occasionally tack it with 309L or 312 filler after preheating, but structural or leak-tight welds should be made in 410 or 304L.
- Does 416 stainless rust?
- More readily than any other common stainless. The sulfide inclusions break the passive film, so it needs to be hardened, polished and passivated to resist even indoor humidity well, and it will rust in salt spray, chloride cleaners and marine air. Oil, black oxide or electroless nickel are the usual protections in harsher service.
- What is 416R stainless?
- A barrel-quality version of 416 produced with tighter control of sulfide size and distribution and a specific heat treatment, sold under producer trade names for rifle barrels. It machines and rifles like 416 with fewer inclusion-related surface defects. It is not an ASTM grade, so buy it by the producer name and cert.
Processes that commonly use it
Related materials
Where to verify these values
- ASTM A582
- AMS 5610
- ASM Handbook, Volume 1 and Volume 16 (machining of stainless steels)
- Producer data sheets for 416 bar (Carpenter, Crucible, Ugitech)
