UNS N02201 · W.Nr. 2.4068 (Special Metals and VDM also list 2.4061 for the same alloy) · EN/DIN designation LC-Ni99 (low-carbon nickel); producer designation Nickel LC 99.2 · Ni(+Co) 99.0% min – C 0.02% max – Cu 0.25% max – Fe 0.40% max – Mn 0.35% max – Si 0.35% max – S 0.010% max (ASTM B160 and ASTM B162 Table 1). It is commercially pure nickel; no strengthening alloying element is added. The ONLY compositional difference from Nickel 200 is the carbon ceiling.
The low-carbon version of commercially pure nickel. It is NOT PRECIPITATION HARDENABLE; it takes its strength from cold work only and cannot be hardened by ageing. Because the carbon ceiling is lowered to 0.02%, graphite does not precipitate at the grain boundaries above 315 °C;
Forms
Round bar · flat bar · plate · sheet · strip · tube and pipe (seamless and welded) · wire · forging. All forms are supplied to order.
Standards
AMS 5553 — sheet and strip; the SAE title is ‘Nickel, Sheet and Strip Low (0.02 max) Carbon Annealed’. Because the carbon ceiling is 0.02%, this specification belongs to Nickel 201. · ASTM B160 / ASME SB-160 — rod and bar. · ASTM B161 / ASME SB-161 — seamless pipe and tube. · ASTM B162 / ASME SB-162 — plate, sheet and strip. · ASTM B163 / ASME SB-163 — condenser and heat-exchanger tube. · ASTM B725 / ASME SB-725 — welded pipe. · ASTM B730 / ASME SB-730 — welded tube. · ASTM B751, B775, B829 — general requirements for tubular products. · ASTM B366 / ASME SB-366 — welded fittings. · DIN 17740, 17750, 17751, 17752, 17753, 17754 · ISO 6207, 6208, 9723, 9724, 9725 · BS 3072, 3073, 3074, 3076 (NA12) · VdTUV 345. ASTM B564 TRAP: the scope list of ASTM B564 (nickel alloy forgings) DOES include N02200 but DOES NOT include N02201. Many sales pages list Nickel 201 forgings under B564; that is wrong.
Advantage
Lowering the carbon ceiling from 0.15% to 0.02% removes graphite precipitation at the grain boundaries above 315 °C and the embrittlement that follows from it.
Welding
Filler metal: Special Metals Nickel Filler Metal 61 (gas tungsten arc and gas metal arc) and Nickel Welding Electrode 141 (shielded metal arc) — the same consumables as Nickel 200. The oxyacetylene process is NOT applicable to Nickel 201 (Special Metals). Preheat is not normally required;
Limits
NOT PRECIPITATION HARDENABLE: there is no solution treatment plus ageing step (nothing like H900 or H1025); strength rises only with cold work. · SPECIFICATION MINIMUMS ARE LOWER THAN NICKEL 200: in ASTM B162, annealed plate, sheet and strip requires 345 MPa tensile and 80 MPa yield for N02201 against 380 MPa and 100 MPa for N02200.
Nickel 201, also known as Alloy 201, is a commercially pure nickel material. Very close to Nickel 200, it is the low-carbon version of that grade — the same kind of carbon difference that separates 316 and 316L among stainless steels. Its UNS designation is N02201 and it consists of at least 99% nickel.
It is also designated 2.4061 and 2.4068. Because Alloy 201 contains less carbon than Alloy 200, it is the better choice for cold worked parts and for parts that need a softer surface. A higher carbon content also lowers corrosion resistance, as it does in stainless steels, so the lower-carbon Nickel 201 has slightly better corrosion resistance than Nickel 200. Its low-carbon structure is also why Alloy 201 is preferred over Nickel 200 in service above 315 °C.
The applications of Alloy 201 closely mirror those of Alloy 200. Used in demanding service, it is the choice where corrosion resistance is the first priority and where the temperature exceeds 315 °C. Among its many uses, electronic components are another common application area.
Chemical Composition · Nickel 201 (2.4061 – 2.4068)
DEFENCE METAL
Ni+Co
min 99.0%
Fe
max 0.40%
C
max 0.02%
Mn
max 0.35%
Si
max 0.35%
S
max 0.01%
Cu
max 0.25%
Mechanical Properties at Room Temperature
DEFENCE METAL
Density (specific gravity)
8890 kg/m³
Melting Temperature
1435 – 1446 °C
Standards and Equivalents · Nickel 201
DEFENCE METAL
Trade name
Nickel 201
UNS
N02201
W.Nr (DIN/EN)
2.4061 · 2.4068
AMS
5553
Available forms
Round bar · Flat bar · Plate · Sheet · Tube · Forgings All forms are supplied to order.
What Nickel 201 Is — and Why It Is a Separate Grade
Nickel 201 (UNS N02201 / W.Nr. 2.4068 / “LC-Ni 99”) is the low-carbon sibling of Nickel 200. Under the ASTM/ASME system the two grades are chemically identical in every element except carbon: Ni (+Co) ≥99.0%, Cu ≤0.25%, Fe ≤0.40%, Mn ≤0.35%, Si ≤0.35%, S ≤0.010% — and C: ≤0.15% in 200, ≤0.02% in 201. That is the only difference, and it is the difference between 315 °C and 677 °C under ASME Section VIII Division 1. 362 °C for a 0.13% carbon difference — which is why 201 costs more.
The mechanism is solubility. Carbon’s solubility in nickel is about 0.2% at 1300 °C and falls to roughly 0.03% towards 315 °C. Nickel 200 at 0.15% C is heavily supersaturated at service temperature; Nickel 201 at 0.02% C is at or below saturation and has nothing to precipitate.(The numeric solubility figures could not be verified in a primary document; the mechanism is verified, so do not publish the numbers as sourced.) The mill states it plainly: “Nickel 201 is not subject to embrittlement by intergranularly precipitated carbon or graphite when held at temperatures of 600 to 1400 °F (315 to 760 °C).“
But this is the most important sentence on the page: low carbon solves graphitisation; it does not solve sulphur embrittlement. Writing about Nickel 201 itself, the mill states that “the material is subject to intergranular embrittlement by sulfur compounds at temperatures above 600 °F (315 °C)“. The Ni–S eutectic melts at 635 °C. The consequence is the mill’s own recommendation: in high-temperature caustic applications where sulphur is present, Inconel 600 is used rather than Nickel 201.
Standards by Product Form · Nickel 201 (N02201 / 2.4068)
DEFENCE METAL
Plate · sheet · strip
ASTM B162 / ASME SB-162 — the scope text explicitly reads “rolled nickel (UNS N02200) and low-carbon nickel (UNS N02201) plate, sheet, and strip”
Rod and bar
ASTM B160 / SB-160 — N02200, N02201 and N02211
ASTM B725 / SB-725 — its title names N02201 explicitly
Welded tube
ASTM B730 / SB-730
Fittings
ASTM B366 / SB-366 — the standard itself is verified; N02201’s inclusion could be verified only at distributor level
FORGINGS
ASTM B564 does NOT cover N02201. This is the most commercially valuable finding on this page — see the section below
Aerospace, 201 only
SAE AMS 5553 — “Nickel, Sheet and Strip, Low (0.02 max) Carbon, Annealed”; current revision AMS5553J. This specification is for N02201 only and cannot be used for 200
There is NO ASTM wire specification (B160 is “Rod and Bar”). The routes are DIN 17753 or ISO 9724
Welding consumables
Same as Nickel 200: bare wire AWS A5.14 ERNi-1 (N02061, EN ISO 18274 S Ni 2061 / NiTi3) · covered electrode AWS A5.11 ENi-1 (W82141). The filler is inherently low-carbon and is not subject to graphite precipitation
Europe
W.Nr. 2.4068. A naming divergence: one mill calls it “LC-Nickel 99.2”, two other sources call it “LC-Ni 99“. 2.4061 = LC-Ni 99.6 is a separate, purer grade with no UNS equivalent
DIN · ISO · BS
DIN 17740/17750/17751/17752/17753/17754 · ISO 6208/6207/9723/9724/9725 · BS NA12. The DIN numbers are historic; current EN replacements could not be verified — quote W.Nr. plus ASTM
ASME temperature limit
Section VIII Div. 1: 1250 °F (677 °C) in five publishers. There is disagreement: one publisher gives 1230 °F, another 1200 °F (the latter is a proprietary variant’s page and reads as an application limit, not a Code limit). The majority is 1250 °F by 5:1:1 — but Section II Part D is paywalled and we could not read it. Verify before stamping a Code number
Do NOT claim
ASME Section I (power boiler) — unverified · NACE MR0175 / ISO 15156 — N02201 is not in the listing we fetched · FDA food-contact approval — there is none
The ASTM B564 Trap — the Most Expensive Paperwork Error
ASTM B564, “Nickel Alloy Forgings,” does not cover UNS N02201. In two independent publishers quoting the scope paragraph, the grades are listed as N02200, N04400, N06600, N06603, N06690, N06625, N06219, N10276, N06022 and some thirty others — N02201 does not appear.
Where the error comes from: the mill’s own bulletin prints its specification table under a combined “Nickel 200 and 201” heading with “Forgings: ASTM B564 / ASME SB-564” on a single line. That is true for 200 and not for 201 — and everyone downstream copied the table without splitting it. The result: Nickel 201 forgings and B564 flanges are routinely advertised against a specification that does not contain the grade.
The caveat we must state honestly: we could not open the B564-22 full text (403), and ASTM’s own page 404’d. This finding rests on two publishers quoting the scope, not on the standard itself. Confirm against the live standard before publishing it — but it is the most commercially valuable finding in this material and it is very likely correct.
If you need low-carbon nickel forgings, the routes are:(1) buy a B564 N02200 forging with a supplementary purchase-order restriction of C ≤0.02% and have the mill certificate show it; or (2) forge from B160 bar and certify to B160’s N02201 chemistry and mechanicals. Either way, the specification called on the certificate must be one that actually contains the grade.
Two related traps from the same table:ASTM B160 is “Nickel Rod and Bar” — it is not a wire specification, so “B160 wire” cannot be certified; wire goes to DIN 17753 or ISO 9724. And B163 is seamless condenser and heat-exchanger tube while B366 is fittings; several suppliers publish “B163 — fittings”, which is simply wrong. One serious distributor prints “B5643 / SB5643” in both its web page and its PDF datasheet — there is no such standard, which shows how little these tables are checked.
Dual Certification 200/201 — Legitimate, But It Proves Less Than Buyers Think
It is legitimate, and it is the normal commercial condition of plate. Suppliers write that “Nickel 200 (UNS N02200) and 201 (UNS N02201) plate are dual-certifiable wrought nickel materials”. The general principle is uncontroversial too: carbon-limit-based dual certification is “the most common legitimate form“, and it has been standard practice since AOD refinement eliminated the cost differential.
The test a heat must pass is two-sided, and the second half is the one people forget:(1) carbon ≤0.02% (meets N02201), AND(2) the mechanical properties must meet N02200’s higher minimums — 380 MPa tensile and 100 MPa yield, not 201’s 345/80. That second condition is the real constraint, because low carbon makes the metal softer. A heat at 0.02% C that only makes 360 MPa is a legitimate Nickel 201 and is not dual-certifiable.
Dual Certification · What It Proves and What It Does Not
DEFENCE METAL
What it proves
That the plate has C ≤0.02% — so it is graphitisation-resistant and may be used to 201’s temperature limits — and that it is strong enough to be designed using 200’s allowable stresses
What it does not 1
It does not upgrade the ASME temperature limit by itself. If the vessel is stamped as SB-162 N02200, the Code limit that applies is N02200’s. To design above it you must specify and stamp the material as N02201. The certificate is not the design basis; the material designation on the U-1A is
What it does not 2
It does not exist for every product form. Plate is routinely dual-certified. ASTM B564 forgings cannot be dual-certified to 201 at all — N02201 is not in B564
What it does not 3
It does not mean “better in all respects”. Dual-certified plate sits at the soft end of the 200 range. If the designer picked 200 for its higher yield, stock at 0.02% C will still pass but will sit near the minimum
What it does not 4
It says nothing about sulphur embrittlement resistance, nor about the anneal / stress-relief condition that caustic service needs
The Caustic Evaporator — What 201 Is Really For
The caustic answer and the temperature answer are the same answer. Caustic evaporators — final-effect evaporators, concentrators and molten-caustic pots — are the classic duty that runs above the 315 °C line. One source says it directly: for above 315 °C (600 °F) “the recommended material is low carbon grade Nickel alloy 201“. So 201 is the caustic-evaporator grade because caustic evaporators are hot — and a graphitised 200 tube sheet in an evaporator is a brittle tube sheet.
Caustic Service · The Numbers and the Two Poisons
DEFENCE METAL
Base behaviour
“Excellent resistance to all concentrations up to and including the molten state. Below 50%, rates are negligible, even in boiling solutions.” The mechanism is a black nickel-oxide film that forms in service
Published envelope (201)
Only above 75% NaOH and near the boiling point does the rate exceed 1 mpy (0.025 mm/a)
Worked example
420–445 °C in technical-grade flake caustic: 21 mpy (0.53 mm/a) in the first 24 h while the film forms, falling to 2.8 mpy (0.07 mm/a) by the end of the week. 50% NaOH at 100 °C: 0.7 mpy (0.018 mm/a)
Where nickel starts
Independent industry handbook: carbon steel max 49 °C, 304L/316L to 93 °C, and “at temperatures above 200 °F, nickel is typically used“
Poison 1 — chlorates
Nickel 200 in 73–96% caustic: 260 mpy (6.60 mm/a) with chlorates versus 1.5 mpy (0.038 mm/a) without — 170×. “Every effort should be made to remove as much of them as possible.” One mill gives the mechanism: chlorate “promotes corrosion attacks through chloride formation“
Poison 2 — oxidisable sulphur
Sodium sulphide in 75% NaOH: 22.8 mpy (0.58 mm/a) versus 0.6 mpy (0.015 mm/a) clean — about 38×. The remedy: “adding sufficient sodium peroxide to oxidize these sulfur compounds to sulfates“
Delivery condition
Annealed. You want a clean, uniform, fully recrystallised surface for the protective film to grow on
Caustic PWHT
700–705 °C, ½ h per 25 mm of thickness, cooled at 90 °C/h — the standard safeguard against corrosion cracking in caustic service
Sources disagree
One European mill states that “heat treatments are normally not required either before or after welding” and offers an optional 550–650 °C, 30 min–3 h low-tension anneal — a range in which “the material does not recrystallize“. These are NOT the same treatment. 700–705 °C is the caustic-specific anti-cracking treatment; 550–650 °C is a general forming stress relief. Do not average them, and do not let a 550 °C treatment be delivered against a caustic-service order
Minimum Mechanical Properties — Why 201 Is Softer
TYPICAL · N02201 rod and bar, hot-finished and annealed
—
70-170
345-415
40-60%
TYPICAL · N02201 rod and bar, cold drawn
—
240-620
415-690
10-35%
The ASTM rows are SPECIFICATION MINIMUMS and are for room temperature. Because N02201 is not precipitation hardenable, the rows are split by PRODUCT FORM and TEMPER (annealed, hot-worked, as-rolled, cold drawn), not by ageing condition. N02200 (Nickel 200) rows are included for comparison; the two alloys sit in the same ASTM specification on separate rows. The last two rows marked TYPICAL are producer typical values and are not specification minimums. The ksi values are those given in the specification text; the MPa values are the specification’s own bracketed equivalents. In the chart, a value given as a range is drawn at its lower bound; the full range is in the table. The ASTM rows are SPECIFICATION MINIMUMS and must not be confused with the TYPICAL rows. In this alloy hardness and strength do not vary with an ageing condition — it is not precipitation hardenable. The variables are product form and the degree of cold work. The N02200 rows are for comparison only; those values cannot be demanded when ordering Nickel 201. No single numerical hardness value (HRB/HB) for annealed Nickel 201 was found in four independent sources, so the hardness columns are empty.
201 is lower by exactly 5 ksi tensile (35 MPa) and 3 ksi yield (20 MPa) across every row. The annealed elongation minimum, however, is identical (40%). A European mill states the reason plainly: “The lowered C-concentration reduces strength and the work hardening rate, and it raises ductility.” That has two commercial consequences: (1) building a vessel in 201 that was designed on 200’s allowables leaves it under-strength; (2) 201 cold-forms better than 200 — lower work-hardening rate, higher ductility.
380 MPa / 100 MPa on the same rows. The gap is constant everywhere: 35 MPa tensile, 20 MPa yield
Deep drawing and spinning
For N02201 sheet there are no grain-size requirements at all; only a maximum of HRB 64. (N02200 sheet carries both grain and hardness requirements.) 201 is a spinning and deep-drawing grade
ASTM B161 (Seamless Pipe/Tube) and B160 (Rod/Bar) · N02201 Minima
Two independent mirrors of B161 give the same numbers but swap the condition labels. The reading above is the metallurgically consistent one (annealed = the soft condition). Confirm against the live standard
B161 mandatory testing
Hydrostatic test on every tube, and a nondestructive electric test per B829
Code-approved to 677 °C — but nearly strengthless there
This is the most abused number on the page.1250 °F (677 °C) is an ASME pressure-retaining limit, not a mechanical capability. A European mill’s own elevated-temperature data for Nickel 201 (Rp0.2 / Rm, MPa): 100 °C: 70/290 · 200 °C: 65/275 · 300 °C: 60/260 · 400 °C: 55/240 · 500 °C: 50/210 · 600 °C: 40/150. Note the collapse above 500 °C. Nickel 201 may be Code-approved to 677 °C, but it is nearly strengthless there; as the temperature rises, calculate your wall thickness from the allowable stress, not from “the Code says 677 °C”.
Physical Properties — Where 201 Beats 200
COMPARISON
Within the same product family there is only one distinction: the CARBON CEILING and the maximum service temperature that follows from it. The carbon ceilings come from ASTM B160 and B162 Table 1; the temperature limits from seven independent producer and distributor sources; the mechanical minimums from ASTM B162 Table 2. Both grades are commercially pure nickel and NEITHER is precipitation hardenable.
DEFENCE METAL
Grade
UNS
W.-Nr.
EN designation
Carbon ceiling
Maximum service temperature
Annealed plate tensile MPa
Annealed plate yield MPa
Reason
Source
Nickel 201
N02201
2.4068 (Special Metals and VDM also 2.4061)
LC-Ni99 (low-carbon nickel)
0.02% max (ASTM B160 and B162)
This is the grade used for service above 315 °C. As a pressure-retaining material it is approved to 677 °C (1250 °F) under ASME Boiler and Pressure Vessel Code Section VIII Division 1.
345
80
Because carbon is held to 0.02%, graphite does not precipitate at the grain boundaries and the material does not embrittle at elevated temperature. Its lower base hardness and work-hardening rate also suit it to spinning and deep cold forming. The price is lower specification minimums.
ASTM B160, ASTM B162, Special Metals, Corrosion Materials, VDM Metals, METALCOR, High Performance Alloys, Alloy Wire International, UPMET
Nickel 200
N02200
2.4066 (Special Metals also 2.4060)
(S-)Ni99.6 — producer designation Nickel 99.2
0.15% max (ASTM B160 and B162)
315 °C (600 °F)
380
100
On prolonged exposure above 315 °C the higher carbon precipitates as graphite and weakens the grain boundaries. In return its specification minimums are higher than those of N02201.
ASTM B160, ASTM B162, Special Metals, Corrosion Materials, Carpenter Technology (via High Temp Metals), Double Eagle Alloys, METALCOR
DEFENCE METAL
Additional information
Tek kritik fark
The ONLY critical difference between Nickel 201 and Nickel 200 is the carbon ceiling: 0.02% against 0.15%. The nickel, copper, iron, manganese, silicon and sulfur limits are the SAME for both grades (ASTM B160 and B162 Table 1). That difference is decisive above 315 °C because of graphite precipitation and embrittlement; below it, it changes only the specification minimums and the formability.
Siparis notu
Much of the material on the market is DUAL CERTIFIED to N02200/N02201. Dual-certified material has carbon below 0.02%, that is, it is in fact Nickel 201. When Nickel 201 is ordered, dual-certified material is acceptable; THE REVERSE IS NOT TRUE — dual-certified material does not meet the higher Nickel 200 specification minimums.
Same criterion, same specification, same product form: the ASTM B162 annealed plate/sheet/strip rows. NEITHER grade is precipitation hardenable. The difference between them is not a heat-treatment difference but a carbon-ceiling difference. The numbers have not been averaged; each row carries its own specification value. This diagram rests on the same numbers as the comparison diagram in spec/nikel-200.json, seen from the opposite direction.
79.3 W/m·K against Nickel 200’s 70.3. 201 conducts better: less carbon, less electron scattering. That is the opposite of what buyers assume from “201 is the cheaper-looking spec”. For context: roughly 4–5× austenitic stainless
Electrical resistivity
0.085 µΩ·m (8.5 µΩ·cm) against Nickel 200’s 0.096. 201 conducts better here too
456 J/kg·K — the same; the curve has a maximum at 358 °C
Thermal expansion 20–100 °C
13.3 × 10⁻⁶ /K — the same
Curie temperature
360 °C / 680 °F — 201 is ferromagnetic too. Saturation flux density 0.61 T. The assumption that “nickel alloys are non-magnetic” is wrong for this grade as well
Structure
FCC austenite from absolute zero to melting — no phase transformation, no hardening by quenching, no ductile-brittle transition
Do not publish
One publisher prints 44 W/m·K for Nickel 200 against four publishers at 70–71. 44 W/m·K is an error. And no numeric relative permeability (µr) could be verified for N02200/N02201
Welding — What Is Specific to 201
The consumables are the same: ERNi-1 (N02061, EN ISO 18274 S Ni 2061 / NiTi3) and ENi-1 (W82141). “Nickel filler metal welds (ENi-1 and ERNi-1) are not subject to graphite precipitation and are used for welding both Nickel 200 and 201.” The filler is inherently low carbon; the risk lies in Nickel 200 base metal and its HAZ, not in 201.
Welding · Points Specific to Nickel 201
DEFENCE METAL
⚠ NO OXYACETYLENE
“The oxyacetylene process is not applicable to Nickel 201.” Two independent sources. The reason: the gas flame carburises the metal — and carburising destroys the very low carbon content that defines the grade. A 201 part “repaired” with oxyacetylene is no longer 201. A page that says “both grades weld identically” is wrong, because the process is applicable to Nickel 200
Carbonaceous atmospheres
Same logic: carbonaceous furnace atmospheres and carbon pick-up turn your 201 into something that graphitises
Sulphur embrittlement
Low carbon buys you nothing here. The Ni–S eutectic melts at 635 °C. Cutting oil, grease, fingerprints, marking crayons, sulphur-bearing fuel and rubber are all sources. So are lead, tin, zinc, bismuth, phosphorus and boron. Dedicated brushes, dedicated wheels, thorough degreasing before welding
Preheat · interpass
Preheat not required · maximum interpass 175 °C (one producer is more conservative at 95 °C)
TIG: pure Ar or Ar + max 3% H₂ · GMAW: Ar or Ar-He. Root protection is mandatory
Joint angle
60–70° included angle — wider than steel; the nickel pool does not flow or penetrate
Porosity
Never use pure nickel wire. ERNi-1 carries Ti 2.0–3.5% (its EN name is “NiTi3”) and ENi-1 deposits ~1.60% Ti — these are deoxidisers. Molten nickel dissolves oxygen and nitrogen and rejects them as gas on freezing; “even 0.025% nitrogen will form pores“
PWHT
General service: not required.Caustic service: 700–705 °C, ½ h per 25 mm, cooled at 90 °C/h
Heat Treatment — 201 Anneals Cooler
HEAT TREATMENT — SCHEMATIC
DEFENCE METAL
1 · ANNEALING — the usual delivery condition
Step
1 · ANNEALING — the usual delivery condition
Summary
Recrystallises and softens cold-worked material. It gives no strength increase; it is the standard delivery condition for corrosion service and general use.
Temperature
705-870 °C (1300-1600 °F) — Corrosion Materials, the common Nickel 200/201 band. Special Metals gives no numerical 201 band; it gives the rule: ‘Annealing temperatures should be 50 to 100 °F (30 to 55 °C) lower or times-at-temperature 10 to 20% shorter than for Nickel 200.’ Since the batch annealing band for Nickel 200 is 705-815 °C, that rule corresponds to 650-785 °C. The two bands have not been averaged.
Time
30 minutes to 3 hours for Nickel 200 batch annealing; for Nickel 201 a 10-20% shorter time is recommended (Special Metals). Corrosion Materials notes that time-at-temperature markedly changes the mechanical properties and the structure.
Cooling
Cooling rate is NOT critical. Quenching is not required; it is used only to reduce surface oxide (Special Metals).
Resulting hardness
For specification minimums see the strength table below. No single numerical annealed hardness value was found in four independent sources, so none is given.
DEFENCE METAL
2 · HOT WORKING
Step
2 · HOT WORKING
Summary
Not a heat treatment; it is the forming temperature range. Heavy deformation is carried out in the upper part of the band.
Temperature
650-1230 °C (1200-2250 °F); heavy forming above 870 °C (1600 °F) — Corrosion Materials (common to Nickel 200/201, one independent source).
Time
—
Cooling
—
Resulting hardness
—
DEFENCE METAL
3 · COLD WORKING — the only strengthening route
Step
3 · COLD WORKING — the only strengthening route
Summary
THERE IS NO PRECIPITATION HARDENING. Strength rises only with cold deformation. The base hardness and work-hardening rate of Nickel 201 are lower than those of Nickel 200, which is why it is preferred for spinning and deep cold forming. When intermediate annealing is needed, stage 1 is repeated.
Temperature
Room temperature
Time
—
Cooling
—
Resulting hardness
Cold-drawn bar typically 415-690 MPa tensile and 240-620 MPa yield (High Performance Alloys, typical values — these are not specification minimums).
DEFENCE METAL
4 · SERVICE TEMPERATURE — ABOVE 315 °C IS PERMITTED
Step
4 · SERVICE TEMPERATURE — ABOVE 315 °C IS PERMITTED
Summary
Not a heat treatment stage but the reason this alloy exists. The 0.02% carbon ceiling prevents graphite precipitation above 315 °C (600 °F); Nickel 201 is used in the range where Nickel 200 embrittles. It is approved as a pressure-retaining material up to 677 °C (1250 °F) under ASME Boiler and Pressure Vessel Code Section VIII Division 1.
Temperature
315 °C (600 °F) threshold — Special Metals, Corrosion Materials, VDM Metals (300 °C), METALCOR (300 °C), High Performance Alloys, Alloy Wire International, UPMET. · ASME upper limit 677 °C (1250 °F) — Special Metals, Corrosion Materials, UPMET (three independent sources).
Not a heat treatment stage; an accepted usage limit. Special Metals states that laboratory crucibles which must withstand oxidizing furnace atmospheres up to 1100 °C (2000 °F) are made of Nickel 201. This is a non-pressure-retaining use and must not be confused with the ASME limit.
Temperature
1100 °C (2000 °F) — Special Metals (one independent source)
Time
—
Cooling
—
Resulting hardness
—
The diagram is schematic; the time axis is NOT to scale. No published TTT/CCT curve was used, so no curve is drawn. N02201 is commercially pure low-carbon nickel and is NOT PRECIPITATION HARDENABLE — there is no solution treatment plus ageing step, and the word ‘ageing’ is not used for this alloy. The number of independent sources that give each band numerically is stated beside each stage. Schematic; the time axis is not to scale. NOT PRECIPITATION HARDENABLE — there is no solution treatment plus ageing cycle for this alloy. The 677 °C upper limit was found in three independent sources; the 315 °C threshold in seven. The two numbers do not carry the same confidence. The 1100 °C crucible use comes from a single source and does not apply to pressure-retaining service.
Nickel 201 is not hardenable by heat treatment — the structure is FCC austenite from absolute zero to melting, and cold work is the only strengthening mechanism. Anything sold as “heat-treated Nickel 201 bar” is cold-drawn; ask for the temper, not a heat-treat condition.
The one thing all sources agree on: Nickel 201 anneals COOLER and/or SHORTER than Nickel 200. The US mill gives the rule numerically: “50–100 °F (30–55 °C) lower, or times-at-temperature 10–20% shorter, than for Nickel 200“. A third source says the same thing differently: open annealing 815–925 °C for N02200 versus 760–870 °C for N02201. The practical reason belongs on the page: over-annealing 201 coarsens the grain badly, because there is no carbon to pin the boundaries.
Heat Treatment · Nickel 201
DEFENCE METAL
Annealing — sources disagree
US mill: 30–55 °C lower than Nickel 200’s range (200 overall 705–925 °C) · European mill: 700–850 °C (the same range for both grades) · a third source: open annealing 760–870 °C, closed annealing 705–760 °C · a fourth: 705–870 °C. Do not average them; state which source you are working to
Why cooler
There is no carbon to pin the grain boundaries → over-annealing coarsens the grain quickly
Target grain size
0.025–0.10 mm (ASTM G.S. 7½–3½)
Atmosphere
A sulphur-free environment is essential. Dry hydrogen or dissociated ammonia for bright annealing; avoid carbonaceous atmospheres
Stress relieving
480–705 °C — no recrystallisation
Low-tension anneal (European)
550–650 °C, 30 min–3 h — “in this range the material does not recrystallize“
Caustic-service PWHT
700–705 °C, ½ h per 25 mm, cooled at 90 °C/h — a separate treatment
Embrittlement — NOT in 201
Graphitisation: “Nickel 201 is not subject to embrittlement by intergranularly precipitated carbon or graphite when held at 315–760 °C“. A European mill confirms it in corrosion terms: the very low carbon content “ensures practically a complete absence of grain boundary attacks even above 315 °C“
Embrittlement — YES in 201
Sulphur: intergranular embrittlement above 315 °C in a sulphur-bearing atmosphere — low carbon does not fix it · Liquid metal: contact with molten Pb, Sn, Zn, Bi, at any temperature
Hot working
US mill 650–1230 °C · European mill, narrower and more conservative, 800–1200 °C. A post-hot-form heat treatment is recommended
Cold working
201 cold-forms better than 200 — lower work-hardening rate, higher ductility. The lubricant trap: sulphur-based lubricants are recommended and the same document warns that sulphur embrittles — the lubricant must be completely removed before any heating, annealing or welding
Corrosion — Notes Specific to 201
The corrosion behaviour is largely the same as Nickel 200‘s — outstanding in caustic, resistant to chloride SCC, excellent in flowing seawater; and unsuitable in oxidising conditions, in nitric acid, in concentrated ammonia, in aqueous concentrated HF and in stagnant seawater. See the Nickel 200 page for the full list. What follows is what is specific to 201.
Nickel 201 · Distinguishing Corrosion Notes
DEFENCE METAL
Caustic evaporators
For caustic above 315 °C the recommended material is 201. The caustic answer and the temperature answer are the same answer
Dry chlorine
Nickel 201 is used for chlorination equipment up to 540 °C (1000 °F); suggested service limit 510 °C (950 °F)
Dry HCl gas
Nickel 201 suggested limit 455 °C (850 °F)
Fluorine
A protective fluoride film forms; 201 is preferred at elevated temperature. Ni 201 rates: 400 °C 8.4 mpy · 450 °C 22.8 · 500 °C 61.2 · 600 °C 348 mpy · 700 °C 408 mpy. Note the jump above 500 °C
Anhydrous HF
“Excellent resistance… even at elevated temperatures” — anhydrous; not aqueous concentrated HF (limited to below 80 °C, and 60–65% commercial acid corrodes severely even at room temperature)
Sulphur-bearing service
201 is no better than 200 here. Sulphur embrittlement above 315 °C applies to both grades; the mill’s recommendation is Inconel 600 instead
Sour service
N02201 was not found in the NACE MR0175 / ISO 15156 nickel-alloy listing we fetched — do not claim it
Frequently Asked Questions
I ordered ASTM B564 UNS N02201 flanges and my inspector rejected them. Why?
Because ASTM B564, “Nickel Alloy Forgings,” does not cover UNS N02201. Its scope lists N02200, N04400, N06600, N06603, N06690, N06625 and some thirty others — low-carbon nickel is not among them. There is no such thing as a B564 N02201 forging or flange, however many distributors advertise one.
This error propagates from a genuine source. The mill’s own Nickel 200 & 201 bulletin prints a specification table under a combined “200 and 201” heading with “Forgings: ASTM B564 / ASME SB-564” on one line. It is true for 200 and not for 201, and everyone downstream copied the table without splitting it.
If you need low-carbon nickel forgings, the routes are: buy a B564 N02200 forging with a supplementary purchase-order restriction of C ≤0.02% and have the mill certificate show it; or forge from B160 bar and certify to B160’s N02201 chemistry and mechanicals. Either way the specification called on the certificate must be one that actually contains the grade.(Caveat: we could not open the B564-22 full text; the finding rests on two publishers quoting the scope. Confirm against the live standard.)
Two related traps from the same table.ASTM B160 is “Nickel Rod and Bar” — it is not a wire specification, so “B160 wire” cannot be certified; wire goes to DIN 17753 or ISO 9724. And B163 is seamless condenser and heat-exchanger tube while B366 is fittings; suppliers publishing “B163 — fittings” are simply wrong.
We have dual-certified 200/201 plate. Can we run our vessel at 400 °C?
The certificate alone does not permit it. Dual certification is legitimate and is the normal commercial condition of plate; what it proves is that the heat has C ≤0.02% (so it is graphitisation-resistant) and that it also meets N02200’s higher mechanical minimums (380 MPa tensile / 100 MPa yield). What it does not prove is your vessel’s Code basis. If the vessel is stamped as SB-162 N02200, the applicable ASME limit is N02200’s: 315 °C. To design at 400 °C you must specify the material as N02201 and stamp it as such on the U-1A. The certificate is not the design basis; the material designation is.
Three further cautions.(1) Dual certification does not exist for every product form: plate is routinely dual-certified, but B564 forgings cannot be certified to 201 at all. (2) Dual-certified plate sits at the soft end of the 200 range; if the designer chose 200 for its higher yield, the material passes but sits near the minimum. (3) The certificate says nothing about sulphur embrittlement or the anneal condition — and if you are at 400 °C in a sulphur-bearing atmosphere, carbon was never the right question.
They say 201 is good to 1250 °F (677 °C) — can I design a vessel at 650 °C?
You are reading the number wrong. 1250 °F is an ASME Section VIII Division 1 pressure-retaining limit, not a mechanical capability. A European mill’s own elevated-temperature data (Rp0.2 / Rm, MPa): 100 °C 70/290 · 300 °C 60/260 · 500 °C 50/210 · 600 °C 40/150. At 600 °C the yield strength is 40 MPa. The Code permits it; your wall thickness will pay for it. A vessel at 650 °C can be designed, but it must be calculated from the allowable stress, not from “the Code says 677 °C”.
There is also disagreement about the figure itself: five publishers give 1250 °F (677 °C), one gives 1230 °F, and another 1200 °F (649 °C) — the last being a proprietary variant’s page that reads as an application limit rather than a Code limit. The majority is 1250 °F by 5:1:1, but ASME Section II Part D is paywalled and we could not read it. Verify against Section II Part D before stamping a Code number. Likewise, ASME Section I (power boiler) acceptance is unverified — do not claim it; several distributor pages assert “ASME approved” without naming a Section.
And on the way up to 677 °C, do not forget the second limit:sulphur embrittlement above 315 °C applies to both grades, and low carbon does not fix it. For high-temperature caustic service where sulphur is present, the mill’s recommendation is not Nickel 201 but Inconel 600.
STANDARDS BY PRODUCT FORM
DEFENCE METAL
Product form
Standards
Sheet, strip
AMS 5553 (SAE title: ‘Nickel, Sheet and Strip Low (0.02 Max) Carbon Annealed’ — this number belongs to Nickel 201) · ASTM B162 / ASME SB-162 · DIN 17750 · ISO 6208 · BS 3072, 3073 (NA12) · VdTUV 345
Plate
AMS 5553 does NOT cover plate (sheet and strip only) · ASTM B162 / ASME SB-162 · DIN 17750 · ISO 6208 · VdTUV 345
Round bar, flat bar
NO AMS number (none could be verified for N02201 bar) · ASTM B160 / ASME SB-160 · DIN 17752 · ISO 9723 · BS 3076 (NA12) · VdTUV 345
Tube and pipe — seamless
NO AMS number · ASTM B161 / ASME SB-161 (seamless pipe and tube; the scope names N02200 and N02201 together) · ASTM B163 / ASME SB-163 (condenser and heat-exchanger tube) · ASTM B775 and B829 (general requirements) · DIN 17751 · ISO 6207 · BS 3074 (NA12)
Tube and pipe — welded
NO AMS number · ASTM B725 / ASME SB-725 (welded pipe) · ASTM B730 / ASME SB-730 (welded tube) · ASTM B751 and B775 (general requirements)
Forging
NO AMS number · ASTM B564 DOES NOT COVER THIS ALLOY — the B564 scope list contains N02200 but not N02201 · DIN 17754 and ISO 9725 are used; the acceptance criteria must be set by the purchase order text
Wire, ribbon
AMS 5555 is titled ‘Nickel Wire and Ribbon 99Ni’; the SAE title states no carbon class, so it COULD NOT BE VERIFIED whether it belongs to 200 or 201 · There is no ASTM wire specification; DIN 17753 and ISO 9724 are used
Welded fitting
NO AMS number · ASTM B366 / ASME SB-366 (from the specification list of the Special Metals bulletin; the scope text of this number was not read one by one in this work)
Chemical composition (form independent)
DIN 17740 · UNS N02201 · W.Nr. 2.4068 (and 2.4061)
AMS numbers are given first, ASTM afterwards. The ONLY AMS number that could be verified for Nickel 201 is AMS 5553, and it covers SHEET and STRIP only. The ASTM B564 row is the most important warning on this map: N02201 forgings cannot be ordered under that specification. The scope texts of ASTM B366, B751, B775 and B829 were not read one by one in this session; they come from the specification list of the Special Metals bulletin.
