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Nickel 200 / (2.4060) / UNS N02200

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Nickel 200, also known as Alloy 200, is a commercially pure nickel material. It consists of at least 99% nickel and that figure often reaches as high as 99.6%. Designated UNS N02200, it is known in the DIN system as 2.4060 and 2.4066. It has good mechanical strength. Nickel is already used inside many stainless steels to raise corrosion resistance, and as an essentially pure nickel, Alloy 200 has very good corrosion resistance of its own — it withstands a wide range of corrosive environments. Alongside its very good mechanical properties and corrosion resistance, the magnetic properties, high thermal conductivity and high electrical conductivity of Nickel 200 are what make it the choice in many special-purpose applications.

Like all nickel alloys, Nickel 200 (2.4060 – 2.4066) is expensive and should be specified where it is genuinely required, otherwise costs rise considerably. It is frequently used in food processing machinery components and food lines, in various fibre-industry parts, and wherever corrosion resistance has to be at its highest. It should be chosen where corrosion resistance is the first and most important priority in the service environment. It is also used in parts in contact with many chemicals, in chemical tankers, in various electronic components and in the aerospace sector.​‌​​‌​

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What Nickel 200 Is — and the First Correction

Nickel 200 (UNS N02200 / W.Nr. 2.4066 / “Ni 99.2”) is commercially pure wrought nickel: Ni (+Co) ≥99.0%. Two things on this page deserve unusually careful reading. First, carbon. The only chemical difference between Nickel 200 and Nickel 201 is carbon (0.15% max versus 0.02% max), and that single difference is the difference between 315 °C and 677 °C under ASME Section VIII Division 1. Second, magnetism. Nickel 200 is ferromagnetic at room temperature. Anyone buying on “nickel alloys are non-magnetic” is mistaken — the Curie point is 360 °C and the saturation flux density 0.61 T.​‌​​‌​

ASTM N02200 and W.Nr. 2.4066 are NOT the same chemistry. Almost every datasheet prints them on one line, and this is the most common standards error in this material. 2.4066 is tighter: C ≤0.10% (ASTM 0.15), S ≤0.005% (ASTM 0.010), Si ≤0.15% (ASTM 0.35), plus Ti ≤0.10% and Mg ≤0.15% limits that ASTM simply does not have. The consequence: a heat at 0.13% C and 0.008% S is fully compliant with ASTM B162 and fails 2.4066 on two counts. If your customer’s drawing says 2.4066 — as German, Turkish and most EU chemical-plant drawings do — an ASTM-only certificate is not automatically acceptable.

The Carbon Line — the Centrepiece of This Page

What 315 °C is, and what it is not​‌​​‌​

The commonly quoted figure is 600 °F / 315 °C, and it holds up — but the sources do not all mean the same thing by it, and one major European mill gives a different number. The US mill bulletin: Nickel 200 is “normally limited to service at temperatures below 600 °F (315 °C)“. Against that, VDM Metals sets its own switch-over at 300 °C (572 °F): “In application temperatures above 300 °C, VDM Nickel 201 is preferable over VDM Nickel 200” — while elsewhere in the same document quoting 315 °C. Verdict: publish 315 °C as the ASTM/ASME line and 300 °C as the conservative design line for anything built to an EU drawing (2.4066/2.4068). Do not present 315 °C as universal.

There is also a third, quite different justification in circulation: a wire producer gives the same 315 °C for strength, not graphitisation — “tensile strength and elongation drop significantly at temperatures above 315 °C”. Three sources, one number, three reasons; state which reason you are invoking.​‌​​‌​

The mechanism: the damage does not happen at 315 °C

The failure is not an event that occurs at 315 °C. It is precipitation of carbon at the grain boundaries — as carbide, and as carbide that decomposes to graphite — during prolonged exposure in a hotter window, which leaves the part brittle once it is cooled and loaded. The mill states the window explicitly: prolonged exposure at 425–650 °C (800–1200 °F) causes “graphitization which can result in severely compromised properties“.​‌​​‌​

Three practical consequences your page should state. (1) 315 °C is the entry to the risk zone, not the point of failure. Damage accumulates fastest at 425–650 °C; a vessel that spends its life at 350 °C degrades slowly, one that sits at 500 °C degrades fast. (2) It is time-dependent. “Prolonged exposure” — none of the sources fetched gives a time–temperature curve for onset. Do not publish an invented one. (3) There is no problem in the weld metal. ENi-1 and ERNi-1 welds are not subject to graphite precipitation and are used to weld both grades; the risk is in the Nickel 200 base metal and the HAZ.

The second embrittlement — and low carbon does NOT fix it​‌​​‌​

A different failure mode with the same threshold temperature: the mill, writing about Nickel 201 itself, states that “the material is subject to intergranular embrittlement by sulfur compounds at temperatures above 600 °F (315 °C)“. Low carbon buys you nothing against it. The Ni–S eutectic melts at 635 °C (1175 °F) — far below any hot-working or annealing temperature — so sulphur picked up from fuel, lubricant, a marking crayon or a dirty glove liquates the grain boundaries. The mill’s own conclusion is unambiguous: in high-temperature caustic applications where sulphur is present, Inconel 600 is used rather than Nickel 201.

Heating-fuel limits (single-sourced): sulphur-free gas or low-sulphur oil (under 0.5% S); gas not more than 30 grains of total sulphur per 100 cu ft (0.68 g/m³), preferably under 15 grains (0.34 g/m³). The material is also “sensitive to intergranular attack from sulfur and metals such as lead, tin, zinc, and bismuth that have low melting points”. A European mill confirms independently: “Sulfur, phosphorus, lead and other low-melting point metals can result in material damage during heat treatment“.​‌​​‌​

Chemical Composition — the ASTM / EN Divergence

Minimum Mechanical Properties — Specification Minima, Not Mill Typicals

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The values below are the ones a designer may use. They are lower than anything a mill will actually ship. Most supplier pages blur this distinction, and designing to a typical range as though it were a minimum is a real error.​‌​​‌​

Typical (mill) properties — NOT design minima​‌​​‌​

Nickel 200, room temperature, typical ranges (MPa): rod/bar hot-finished 415–585 tensile / 105–310 yield · rod/bar cold-drawn 450–760 / 275–690 · rod/bar annealed 380–520 / 105–210 · plate hot-rolled 380–690 / 140–550 · plate hot-rolled + annealed 380–550 / 105–275 · sheet annealed 380–520 / 105–210 · sheet hard 620–795 / 480–725 · strip spring temper 620–895 / 480–795 · tubing annealed 380–520 / 85–210 · tubing stress-relieved 450–760 / 275–620 · wire annealed 380–580 / 105–345 · wire spring temper 860–1000 / 725–930. European mill typical annealed values: Rp0.2 100 MPa, Rp1.0 125 MPa, Rm 370 MPa, A 40%, hardness <130 HBW.

One thing not to publish: the mill bulletin’s typical hardness rows for rod and bar are labelled HRB but contain values above 100 HRB (e.g. “HRB 140–230”). Those are almost certainly Brinell/Vickers numbers in the wrong column. Re-check them before publishing any of those hardness figures.​‌​​‌​

Cryogenic behaviour — the alloy’s quiet advantage

Nickel 200 is FCC austenitic from absolute zero to melting and has no ductile-to-brittle transition. At −255 °C (−423 °F): 60% elongation, 70% reduction of area; at −185 °C (−300 °F): 690 MPa (100 ksi) tensile, 53% elongation. Charpy V-notch: hot-rolled 163 J · cold-drawn + stress-relieved 204 J · cold-drawn + annealed 228 J.​‌​​‌​

Physical Properties — and Magnetism

The sentence your page needs about magnetism: below 360 °C it is magnetic; above 360 °C it is not. Note how close that transition sits to the 200→201 switch-over (300–315 °C): a Nickel 200 part running at its temperature limit is also close to its magnetic transition, with both its magnetic and its thermal properties changing there. This disqualifies the material from MRI, magnetometer and some instrumentation service.

Welding​‌​​‌​

Welding pitfalls — in order of how often they bite​‌​​‌​

1. SULPHUR EMBRITTLEMENT — the number one killer. The Ni–S eutectic melts at 635 °C, so any sulphur on the surface when the metal gets hot liquates the grain boundaries and cracks the joint or the HAZ. Sources: cutting oil, grease, fingerprints, marking crayons and paints, sulphur-bearing fuels, rubber. Also lead, tin, zinc, bismuth, phosphorus and boron. The remedy: “stainless steel wire brushing followed by thorough degreasing with a suitable solvent is necessary before welding“, and “maximum cleanliness is required; tools that have been used for other materials may not be used for nickel alloys and stainless steels“. Dedicated brushes, dedicated grinding wheels, no exceptions.
2. Porosity — from an undeoxidised filler, from lost gas shielding, or from moisture. Covered electrodes: “excessive exposure of electrodes to humid conditions will cause some moisture pick-up and increase the risk of porosity”.
3. A sluggish, shallow-penetrating pool — which is why the included angle is 60–70°.
4. Carburisation of Nickel 201 by oxyacetylene or a carbonaceous atmosphere — it turns your 201 into something that graphitises.
5. Weld-metal graphitisation is NOT a risk — the filler is inherently low carbon. The risk is in the Nickel 200 base metal and HAZ.

Heat Treatment​‌​​‌​

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Neither grade is hardenable by heat treatment. Cold work is the only strengthening mechanism. The structure is FCC austenite from absolute zero to melting — there is no transformation to exploit and no precipitate to age. Anything sold as “heat-treated” or “hardened” Nickel 200 bar is cold-drawn, or cold-drawn and stress-equalised. Ask for the temper, not a heat-treat condition.

Machining

Corrosion — Where It Is Strong and Where It Is Not

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Frequently Asked Questions​‌​​‌​

Nickel 200 or Nickel 201? At what temperature does the answer change, and what fails if I get it wrong?

Order Nickel 200 for service below 315 °C (600 °F) and Nickel 201 above it. One European mill sets its own switch-over at 300 °C (572 °F), so if your drawing is to W.Nr. 2.4066/2.4068 rather than UNS, use 300 °C as the design line. The only chemical difference is carbon: 0.15% max in 200, 0.02% max in 201. At 0.15%, Nickel 200 is heavily supersaturated in carbon at service temperature. On prolonged exposure — fastest in the 425–650 °C band — that carbon precipitates at the grain boundaries as carbide and graphite, and the boundaries become a continuous brittle film. The part does not lose section and it does not leak; it loses toughness, then cracks under thermal shock, bolt-up or a pressure excursion. Inspection will not find it before it fails, because nothing is corroding. Getting it wrong the other way is merely expensive: Nickel 201 is softer (ASTM B162 minima 345 MPa tensile / 80 MPa yield versus 380 / 100 for Nickel 200), so a vessel designed on 200’s allowables and built in 201 is under-strength. The commercial consequence is the ASME limit: under Section VIII Division 1, Nickel 200 is accepted to 315 °C and Nickel 201 to 677 °C. Verify against Section II Part D before stamping — we could not read that Code figure from the primary document.​‌​​‌​

For caustic service, what heat treatment and stress relief must I specify, and why?

Specify three things, not one.
First, the grade. Below 95 °C carbon steel or 316L will do; above 95 °C, nickel is the standard material. If the equipment runs above 315 °C — most final-effect evaporators, concentrators and molten-caustic service — it must be Nickel 201, not 200, because those are exactly the temperatures at which Nickel 200 graphitises.
Second, the delivery condition: annealed. Nickel’s caustic resistance depends on a black nickel-oxide film that builds in service. In one documented test at 420–445 °C the rate started at 21 mpy while the film formed and settled at 2.8 mpy within a week. You want a clean, uniform, fully recrystallised surface for that film to grow on.
Third, post-weld stress relief — and be precise, because two different treatments get called by the same name. The caustic-specific anti-cracking treatment is 700–705 °C for ½ hour per 25 mm of thickness, cooled at 90 °C per hour. That is not the same as the 550–650 °C low-tension anneal used to take forming stresses out of cold-worked material, which deliberately stays below recrystallisation. One European mill’s position is that PWHT is not normally required for ordinary service — so state “caustic service” on the purchase order or you will not get it. Do not average the two treatments, and do not let a 550 °C treatment be delivered against a caustic-service order.
Finally, control the caustic itself: chlorates take Nickel 200 in 73–96% NaOH from 1.5 to 260 mpy; sodium sulphide takes it from 0.6 to 22.8 mpy in 75% NaOH.​‌​​‌​

We bought “non-magnetic nickel” and a magnet sticks to it — is it the wrong material?

No. Nickel 200 and 201 are ferromagnetic at room temperature, and this is not a footnote but a material property: Curie temperature 360 °C / 680 °F, saturation flux density 0.61 T. The misconception comes from generalising “nickel alloy = non-magnetic” out of experience with austenitic stainless and Inconel; for commercially pure nickel that is simply wrong. Three practical consequences. (1) Below 360 °C it is magnetic, above it is not — and note how close that transition sits to the 200→201 switch-over (300–315 °C): a Nickel 200 part at its temperature limit is also at the foot of its magnetic transition. The distinct maximum in the specific-heat curve at 358 °C and the kink in the thermal-conductivity curve in the 300–400 °C region are traces of the same event. (2) It is magnetostrictive (30 × 10⁻⁶ ΔL/L) — not a defect but a genuine application: ultrasonic transducers. (3) No heat treatment fixes it; the material is FCC austenite from absolute zero to melting and the ferromagnetism is electronic, not a second phase. What to do: if the non-magnetic requirement is real, Nickel 200/201 is the wrong material — for MRI, magnetometer and some instrumentation service consider Monel K-500 (permeability ≈1.001–1.002) or an austenitic grade. And do not trust a datasheet that hands you a numeric permeability for N02200 — four independent publishers give the Curie point and the saturation flux density, and none gives a numeric µr.​‌​​‌​

“ASTM B160 wire” and “FDA approved” — why are both of those a problem?

Both are wrong, and both are everywhere.
ASTM B160 is not a wire specification. It is titled “Nickel Rod and Bar” and its scope is “round, square, hexagonal, or rectangular solid sections“. There is no ASTM wire specification for N02200/N02201. Even the mill bulletin lists wire only against DIN 17753 / ISO 9724. If a customer asks for ASTM-certified nickel wire, the honest answers are DIN 17753, ISO 9724, or a mill-standard chemistry certificate to B160’s chemical table — not “B160 wire“.
There is no FDA food-contact approval. The FDA food-contact inventory lists “nickel” under 21 CFR 172.864, 176.180 and 184.1537 — but those provisions concern nickel as a hydrogenation catalyst and food additive (including Raney nickel), not Nickel 200/201 as an equipment construction material. A distributor’s “used in food processing equipment” is an application, not an approval. Do not put “FDA approved” on your page; write “widely used in food-processing and synthetic-fibre (viscose/rayon) plant” — that much is verified in three independent publishers. By the same logic, do not quote QQ-N-281 for Nickel 200: that is the federal specification for the nickel-COPPER alloy (Monel 400, N04400) and has nothing to do with commercially pure nickel. We found no live federal or military specification for N02200/N02201; if a customer asks for one, say so rather than substituting another number.​‌​​‌​

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