Guide
When should you specify Nitronic 60 for valve stems and threaded parts?
Nitronic 60 is a nitrogen-strengthened austenitic stainless steel, UNS S21800, alloyed with typically about 8% manganese and 4% silicon so that it resists galling and wear even in the annealed condition. Short answer: specify it when a stainless part slides or threads against stainless under load, such as a valve stem in its packing and bonnet threads, a nut on a stainless stud, or a pin in a bushing, and ordinary 304 or 316 would gall; skip it when a lubricant, a dissimilar mating material or a coating already solves the problem, because it costs more and machines more slowly.
By Saola Manufacturing engineering team · Published · Updated
Galling is the reason most engineers look up Nitronic 60. The general causes and fixes for galled stainless threads are covered in the stainless thread galling guide; this page is about the material choice itself: what the published galling data says, which parts benefit, what specifications cover the alloy, what it is like to machine, and how to write it on a drawing so the right bar arrives.
On this page
What makes Nitronic 60 resist galling?
Its chemistry: high manganese and silicon, plus nitrogen, change how the surfaces behave under sliding contact, so two clean faces resist tearing and cold-welding where 304 and 316 seize. It does this without hardening, which is unusual among anti-galling materials.
The producer's data, reprinted in the HP Alloys Nitronic 60 product data bulletin, lists applications that follow directly from that property: valve stems, seats and trim; fastening systems including nuts and bolts; pins, bushings and roller bearings; and pump wear rings. The same bulletin states that its room-temperature yield strength is nearly twice that of Types 304 and 316, that its uniform corrosion resistance is better than Type 304 in most media, and that its chloride pitting resistance is better than Type 316.
| Element | Minimum (%) | Maximum (%) |
|---|---|---|
| Carbon | 0.060 | 0.080 |
| Manganese | 7.50 | 8.50 |
| Silicon | 3.70 | 4.20 |
| Chromium | 16.00 | 17.00 |
| Nickel | 8.00 | 8.50 |
| Nitrogen | 0.10 | 0.18 |
| Molybdenum | — | 0.75 |
How much better is Nitronic 60 than 304 or 316 in galling tests?
In the producer's unlubricated button-and-block tests, 304 and 316 against themselves galled at the lowest stress tested, while Nitronic 60 against 304, 303 or 17-4 PH did not gall at the highest stress tested. Against 316 and against itself it galled, but only at far higher stresses than the common grades.
The test ranks pairs of materials: a polished button is loaded onto a flat block, turned once by hand, and examined for galling, and the stress is raised until galling appears. The bulletin is clear that the test is for screening alloys, not for design, and the current standard version of this kind of test, ASTM G98-23, makes the same point: it ranks material couples and should not be used for quantitative or final design purposes.
Two practical lessons follow. First, the big gain comes from putting Nitronic 60 on one side of a stainless pair; you do not always need both parts in it. A Nitronic 60 nut on a 304 stud, or a Nitronic 60 stem in a 304 bonnet, uses the best-ranked pairs in the table. Second, 316 is the weakest partner for Nitronic 60 in this data, so if the mating part is 316, test the actual pair before you rely on it.
| Pair (both annealed unless noted) | Threshold galling stress |
|---|---|
| 304 vs 304 | 2 (14) |
| 316 vs 316 | 2 (14) |
| 316 vs 304 | 2 (14) |
| 17-4 PH H 950 vs 17-4 PH H 950 | 2 (14) |
| Nitronic 60 vs 304 | Did not gall at 50 (345) |
| Nitronic 60 vs 303 | Did not gall at 50 (345) |
| Nitronic 60 vs 17-4 PH H 950 | Did not gall at 50 (345) |
| Nitronic 60 vs 316 | 38 (262) |
| Nitronic 60 vs Nitronic 60 | 50 (345) |
Where does Nitronic 60 make sense on a valve or threaded assembly?
Use it on the part that slides or threads under load and is hard to lubricate or inspect: valve stems, stem nuts and bonnet threads, seat rings, pins and bushings, and nuts on stainless studs that must come apart after years in service. It is rarely worth it on a lightly loaded, lubricated or rarely moved joint.
Valve stems are the classic case because the stem slides through packing and threads through a yoke nut or bonnet, often in stainless bodies, with little lubrication and long intervals between movements. Fasteners are the second case, especially large stainless nuts and studs tightened to high preload, where a galled thread means cutting the fastener off. The bulletin also lists ASTM A193 Grade B8S bolting and ASTM A194 Grade 8S nuts as specifications that cover the alloy, which is the path for standard fasteners rather than custom machined parts.
Consider the alternatives before you change the material. An anti-seize compound, a dissimilar pairing such as a bronze nut on a stainless stem, a thread with more clearance, or a coating on one part may solve galling at lower cost. Nitronic 60 is the answer when those are not acceptable: when lubricants are forbidden, when the joint is in a process fluid, or when the part must stay serviceable without maintenance.
What is Nitronic 60 like to machine?
Harder than 304: the bulletin rates it at about half the machinability of Type 304, and it recommends coated carbide tools, sufficient power and rigid setups. Expect a higher machining cost per part than the same part in 304 or 316.
Per ANSI B1112 ratings quoted in the bulletin, where B1112 free-machining steel is 100%, Type 304 rates 45% and Nitronic 60 rates 23%. It work-hardens like other austenitic stainless steels, so light, rubbing cuts and dull tools make things worse; steady feeds and sharp tools matter. Threads deserve particular care because the purpose of the material is a clean, smooth thread flank: a torn or built-up flank on a thread that is meant to resist galling defeats the point.
Material form also changes the cost. Nitronic 60 is produced as bar and forging stock, with other forms such as plate and castings from other producers using licensed melts, according to the bulletin. Bar availability by size varies more than for 304 or 316, so confirm the bar size early.
How should Nitronic 60 be called out on the drawing and RFQ?
Name the UNS number and the product specification, for example "UNS S21800 bar per ASTM A276, annealed", or AMS 5848 for aerospace bar, and require a mill certificate. The trade name alone does not tell the supplier which specification, condition or test applies.
A complete callout carries the grade (UNS S21800), the specification (ASTM A276 for general bar, ASTM A479 for pressure-vessel bar, AMS 5848 for aerospace bar and forgings), the condition (usually annealed, or a high-strength cold-worked level if you need it), and the certificate. The bulletin lists minimum tensile properties under AMS 5848 and higher-strength levels for cold-worked bar, so if strength matters, name the level. Say whether a substitute is allowed; "Nitronic 60 or equivalent" invites a different alloy with different galling behavior.
Add the mating material to the drawing notes or the RFQ. A supplier who knows the stem runs in a 316 bonnet can raise the pairing question; one who sees only the stem drawing cannot.
Can Saola machine parts in Nitronic 60?
Nitronic 60 is not on the bar list of the lead CNC plant's turning page, so the material, grade and bar source are confirmed at drawing review before any quote is firm. The turning and milling themselves are in-house at that plant.
The CNC turning page lists the bar materials run today, and the CNC milling page covers second-operation milling. If your part needs UNS S21800, put the specification and condition on the drawing and say what it mates with; the bar source and certificate route are agreed before the order, and material certification is available on request as described on the quality page. Thread gauging is done with go/no-go gauges. Send drawings through the quote form.
Frequently asked
Is Nitronic 60 the same as Alloy 218?
Yes, both names refer to UNS S21800. Nitronic is a trademark of the producer, so drawings should call the UNS number and specification rather than the brand.
Is Nitronic 60 magnetic?
It is an austenitic grade, but magnetic response depends on condition and cold work. If permeability matters, specify a limit and a test.
Can Nitronic 60 be welded?
The bulletin reports that it is readily welded with conventional processes and that gas tungsten-arc welds keep wear behavior close to the base metal. Confirm the filler metal and any post-weld requirement with the supplier.
Does Nitronic 60 still need anti-seize on threads?
Often not for galling alone, which is the reason to choose it. Many assemblies still use a compatible lubricant for consistent torque-tension, so check your assembly specification.
Is Nitronic 60 more corrosion resistant than 316?
Not in every environment. The producer reports better chloride pitting resistance than 316 and better uniform corrosion than 304, but service conditions vary, so test in your fluid if corrosion is the main risk.
Sources
- NITRONIC 60 Stainless Steel product data bulletin (reprinting producer data; Nitronic is a trademark of AK Steel), HP Alloys, 2011
- ASTM G98-23, Standard Test Method for Galling Resistance of Materials (scope and significance), ASTM International, 2023
- ASTM A276/A276M-25, Standard Specification for Stainless Steel Bars and Shapes, ASTM International, 2025