Nickel 207 (UNS N02207) Technical Guide | Specialized High-Purity Nickel for Aggressive Chemical Service

Nickel 207 (UNS N02207) — High-Purity Nickel for Harsh Chemical Environments | Hangbo Alloy

High-Precision Engineering Reference for Severe-Service Process Equipment, Caustic Systems, and Halogen Service

Introduction

Nickel 207 — registered within the commercially pure wrought-nickel block of the UNS system as N02207 — is the high-purity member of the pure-nickel product family that includes Nickel 200 (UNS N02200) and Nickel 201 (UNS N02201). Where the N02200/N02201 pair is distinguished by carbon content, the N02207 designation identifies the tightly controlled, high-purity branch of the family: a commercially pure nickel matrix with a minimum nickel-plus-cobalt content of 99.0%, carbon disciplined to the low-carbon regime, and residuals held to the tightest practical limits so that the material delivers maximum chemical inertness in the most demanding process environments.

The engineering logic behind a high-purity nickel grade is simple but fundamental. In a harsh chemical environment — hot concentrated caustic, anhydrous hydrofluoric acid service, chlor-alkali cell liquors, hot alkalis carrying sulfur species — corrosion resistance is not delivered by a passive alloying element but by the intrinsic surface behavior of nickel itself. Every fraction of a percent of residual impurity is a potential weak point: a site for selective leaching, a second phase that can be preferentially attacked, or a grain-boundary constituent that can embrittle the metal at temperature. Nickel 207 is specified where that margin matters — where plant designers want the purest practical nickel matrix, controlled to the low-carbon discipline that keeps it safe in elevated-temperature caustic duty, and documented heat by heat so that the delivered material is exactly what the certificate claims.

Shanghai Hangbo Alloy Group supplies Nickel 207 as plate, sheet, strip, round and flat bar, rod, and wire, certified to ASTM B160 (rod, bar, and wire) and ASTM B162 (plate, sheet, and strip), with EN 10204 3.1 mill certification and full heat traceability. This guide provides the engineering data needed to specify, procure, fabricate, and verify N02207 for caustic evaporation, chlor-alkali, halogen-handling, and high-purity chemical plant.

1. Alloy Identity and Metallurgy

The metallurgy of the pure-nickel family explains what Nickel 207 is, and what it is not:

• A matrix of essentially unalloyed nickel. There is no chromium to form a stainless-type passive film and no molybdenum to armor against pitting. Corrosion resistance is intrinsic to the nickel surface, which means there is no alloying element that can be selectively leached and no second phase available for preferential attack. This is precisely the property set that made nickel the reference material for caustic evaporation and chlor-alkali hardware for nearly a century.
• Low-carbon discipline as the safety feature. Carbon is controlled to the 0.02% maximum of the low-carbon regime. This is the same discipline that distinguishes Nickel 201 from Nickel 200: it keeps carbon below the solubility limit so that long residence in the 315–650 °C band cannot precipitate grain-boundary graphite — the embrittlement mechanism known as graphitization that rules out conventional high-carbon nickel in hot caustic service.
• Residual control as the purity argument. Iron, copper, manganese, silicon, and sulfur are held to tight limits so that the material behaves as pure nickel and nothing else. Sulfur control deserves particular attention: sulfur is the classic embrittling impurity in nickel, forming low-melting sulfides that destroy hot workability and high-temperature integrity.
• FCC structure with unmatched formability. Like all pure-nickel grades, the single-phase austenitic structure delivers outstanding deep-drawing, spinning, rolling, and welding behavior — essential for the complex evaporator, cell, and reactor geometries that dominate severe chemical service.

A note on the designation for purchasers: N02207 is less widely catalogued in open literature than the N02200/N02201 pair, and the "Nickel 207" name also circulates in the welding-consumable trade on ENi-1-type pure-nickel electrode products used to join this family. For wrought supply, the engineering discipline is identical to the pure-nickel family and the acceptance basis is the governing product standard — ASTM B160 for rod, bar, and wire and ASTM B162 for plate, sheet, and strip — with every heat documented by actual analysis. Hangbo Alloy therefore certifies the actual measured composition of each N02207 heat and recommends that buyers specify the governing product standard and the required application temperature on the order, so that acceptance rests on the certified values rather than on the designation alone.

2. Governing Specifications — Plate, Sheet, Rod, and Bar

Because the difference between a high-purity nickel grade and an ordinary Nickel 200 heat is invisible to the eye and to handheld analyzers, Hangbo Alloy recommends that every order state the full callout — "Nickel 207 (UNS N02207) plate per ASTM B162, low-carbon regime, EN 10204 3.1" — and that the certificate be reviewed for the UNS number, the product standard, the heat number, and the actual carbon, sulfur, and nickel values. Those four lines of the mill certificate are the entire verification story for high-purity nickel.

3. Chemical Composition — Typical Control Ranges

The table below presents the UNS N02200/N02201 family ranges for reference alongside the typical control ranges applied by Hangbo Alloy to N02207 supply. Because public registry data for the N02207 wrought designation is less extensively published than for N02200/N02201, Hangbo Alloy applies the family's compositional control logic, tightens residuals where the high-purity designation demands it, and reports the actual measured values on every heat's 3.1 certificate.

The three values to verify on every Nickel 207 certificate are nickel-plus-cobalt (99.0% minimum), carbon (0.02% maximum), and sulfur (0.010% maximum, typically far lower). A heat that satisfies those three lines — with actual measured values reported rather than assumed — is a high-purity, low-carbon nickel suitable for the severe services for which the grade is specified. Hangbo Alloy reports all three on every heat and supports independent verification by combustion analysis and ICP where the purchaser requires it.

4. Mechanical Properties

Nickel 207 is supplied in the annealed condition and, for strip and wire, in controlled cold-worked tempers. Representative room-temperature properties as supplied by Hangbo Alloy:

ASTM B160/B162 minimum requirements for annealed product are on the order of 380 MPa (55 ksi) tensile, 105 MPa (15 ksi) yield, and 35–40% elongation depending on section and product form; Hangbo Alloy certifies the actual minimums applicable to each ordered dimension and condition.

For the harsh-chemical-equipment designer, three property characteristics matter more than peak strength:

1. Ductility across the operating spectrum. Pure nickel retains useful ductility from cryogenic temperatures to several hundred degrees Celsius, so severe-service hardware does not face the low-temperature brittleness issues of carbon steel or the intermediate-temperature aging concerns of some precipitation-hardened alloys.
2. Thermal and magnetic predictability. With a Curie temperature near 360 °C and thermal conductivity roughly ten times that of austenitic stainless, pure nickel behaves predictably in heat-transfer and instrumentation service — a design asset in evaporator tubes and cell hardware.
3. Strength by cold work, not by chemistry. Where component stiffness is required, cold-drawn bar and hard-temper strip deliver it; where corrosion resistance is the sole criterion, the annealed condition maximizes ductility for forming and welding. The grade's role is chemical inertness, and design practice reflects that.

5. Corrosion Resistance — The Harsh-Environment Portfolio

Nickel 207 is selected for environments where the combination of high temperature, high concentration, and chemical severity defeats stainless steels and most nickel alloys. The governing principle is identical to the pure-nickel family: outstanding resistance to alkaline and reducing media, with sharp limits in oxidizing media.

The harsh-environment selection story, restated for engineers who must justify the grade to a client:

1. In hot concentrated caustic, nothing beats nickel. Corrosion rates across the full NaOH concentration range are negligible to very low at ambient and moderate temperature, and remain manageable at high temperature — provided the grade is the low-carbon version where the metal will dwell above roughly 300 °C. This single sentence is the entire reason chlor-alkali evaporator trains are built from nickel.
2. Purity removes the weak points. A high-purity matrix eliminates selective-leaching sites and second phases, so the material corrodes uniformly — if at all — rather than pitting or dealloying. In media that contain trace impurities, tight residual control prevents localized attack at heterogeneities.
3. The low-carbon discipline removes the long-term failure mode. Carbon at 0.02% maximum means the 315–650 °C band — startup, shutdown, upset, and steady-state hot zones alike — cannot drive grain-boundary graphitization. The material that goes into the hottest section of the plant stays ductile for the life of the vessel.
4. Oxidizing media are the hard stop. Nitric acid, hot aerated acids, and strongly oxidizing chloride environments attack pure nickel rapidly. The harsh-environment envelope for N02207 is alkaline and reducing — where it is effectively without peer — not oxidizing, where a chromium-bearing alloy is mandatory.

6. Fabrication, Welding, and Heat Treatment

• Hot forming: Pure nickel hot-forms readily across 650–1230 °C, with best results in the 870–1230 °C window. Hot-formed sections should be re-annealed to restore the soft, recrystallized condition.
• Cold forming: Exceptional deep-drawing, spinning, rolling, and bending behavior. Moderate work hardening means heavy reductions may need intermediate annealing; the lack of phase transformation makes severe forming routine.
• Annealing: Typically 705–925 °C with air cooling or water quench. Furnace atmospheres must be sulfur-free — nickel is embrittled by sulfur at temperature — and bright annealing in protective atmosphere preserves the corrosion-service surface.
• Welding: The pure-nickel consumable family applies: ERNi-1 filler wire and ENi-1 covered electrodes produce low-carbon pure-nickel deposits that retain the graphitization immunity and corrosion behavior of the parent metal. This is where the "Ni 207" name meets the base metal in practice — welded Nickel 207 hardware is joined with the same electrode family that the consumable trade labels Ni 207 / ENi-1. Joints must be scrupulously clean of oil, grease, and sulfur-bearing residues; no preheat is normally required.
• Machining: Like all pure-nickel grades, 207 is soft and gummy under the tool. Sharp positive-rake tooling, rigid setups, and generous coolant give the best results; cold-drawn bar is preferred for screw-machine and CNC work.
• Surface condition: For maximum corrosion performance the surface must be clean, free of embedded iron and grinding burns. Hangbo Alloy supplies Nickel 207 with clean, descaled surfaces and, on request, pickled or bright-annealed finishes and PMI verification.

7. Applications

8. Why Buyers Select Hangbo Alloy for Nickel 207

Hangbo Alloy (Shanghai Hangbo Alloy Group, nickel-alloy.com) supplies Nickel 207 across plate, sheet, strip, bar, rod, and wire with:

• Full EN 10204 3.1 certification and heat-lot traceability to the melt;
• Actual measured values reported for the three decisive elements — nickel-plus-cobalt, carbon, and sulfur — on every heat;
• The low-carbon discipline that keeps high-purity nickel safe in elevated-temperature caustic and halogen service;
• Clean, descaled, corrosion-service surfaces with optional bright annealing and pickling;
• Application engineering support for caustic, chlor-alkali, HF, and high-purity process specifications, including matching ERNi-1/ENi-1 consumable recommendations.

Technical FAQ — Nickel 207 (UNS N02207)

1. What is Nickel 207 (UNS N02207)? Nickel 207 is the high-purity member of the commercially pure wrought-nickel family registered in the N022xx block alongside Nickel 200 (N02200) and Nickel 201 (N02201). It is supplied as a commercially pure nickel matrix — 99.0% minimum nickel-plus-cobalt — with carbon held to the low-carbon regime and residuals tightly controlled, for maximum chemical inertness in harsh process environments.

2. What standards cover Nickel 207 plate and bar? The governing product standards are ASTM B162 (plate, sheet, and strip) and ASTM B160 (rod, bar, and wire), with ASME SB-162/SB-160 equivalents. Related pure-nickel product standards include ASTM B161, B725, B751, and B564 for pipe, tube, and forgings.

3. How does Nickel 207 differ from Nickel 200 and Nickel 201? The entire N022xx family shares the same pure-nickel matrix and corrosion behavior. N02207 is positioned as the high-purity, tightly controlled branch: low-carbon discipline like 201 (0.02% carbon maximum), 99.0% minimum nickel-plus-cobalt, and residuals controlled to tight typical levels — with actual values certified on every heat.

4. Why does Nickel 207 carry the low-carbon discipline? Carbon at 0.02% maximum keeps the metal below the carbon solubility limit at service temperatures, so long residence in the 315–650 °C band cannot precipitate grain-boundary graphite — the graphitization mechanism that embrittles high-carbon Nickel 200. This is what makes the grade safe for caustic service above roughly 300 °C.

5. What is graphitization and why does it matter? Graphitization is the slow precipitation of dissolved carbon as graphite at the grain boundaries of nickel during long exposure at roughly 315–650 °C. Because nickel forms no stable carbide at these temperatures, the carbon rejects to the boundaries in elemental form, destroying grain-boundary cohesion and enabling sudden intergranular failure. It is prevented by grade selection — low carbon — rather than detected by inspection.

6. Is the "Ni 207" name also used for welding consumables? Yes. In the welding trade the designation "Ni 207" is associated with ENi-1-type covered electrodes and the pure-nickel filler family (ERNi-1) used to join Nickel 200/201/207 hardware. The weld deposits are themselves low-carbon pure nickel, so welded Nickel 207 fabrications retain the corrosion behavior and graphitization immunity of the parent metal.

7. What harsh environments is Nickel 207 intended for? Hot concentrated caustic soda and potash, caustic evaporation and concentration, chlor-alkali cell liquors, sulfur-bearing hot alkalis, and controlled dry halogen and anhydrous HF service. The common thread is alkaline or reducing chemistry at elevated temperature — the envelope where pure nickel is the reference material.

8. Where should Nickel 207 not be used? In strongly oxidizing media — nitric acid, hot aerated acids, and strongly oxidizing chloride environments — pure nickel corrodes rapidly and a chromium-bearing alloy is required. Nickel 207 must also never be heated in sulfur-bearing atmospheres, because sulfur forms a low-melting nickel-sulfide eutectic that embrittles the metal.

9. How should a purchaser verify that Nickel 207 stock is genuine? Review the EN 10204 3.1 certificate for UNS N02207 and the three decisive values: nickel-plus-cobalt at 99.0% minimum, carbon at 0.02% maximum, and sulfur at 0.010% maximum with the actual measured result reported. Handheld PMI analyzers cannot measure carbon, so the certificate — backed by independent combustion analysis if doubt remains — is the only reliable verification.

10. What product forms and sizes does Hangbo Alloy supply in Nickel 207? Hangbo Alloy supplies plate from 1.0 to 80 mm thick, round bar from 3 to 300 mm diameter, flat, square, and hexagonal bar, sheet and strip, rod, and wire, in the annealed condition and in cold-worked tempers for strip and wire, with EN 10204 3.1 certification and full traceability. Cutting-to-size and surface-finishing services are available.

This technical guide is provided by Hangbo Alloy (Shanghai Hangbo Alloy Group Co., Ltd., nickel-alloy.com) for material-selection and engineering-reference purposes. Data presented are typical engineering values compiled from recognized industry sources and are not a substitute for the governing ASTM specifications, code approvals, or the certified mill test report applicable to each heat. Contact Hangbo Alloy at sales@hangboalloy.com or +86 136 1165 6360 for current stock, certificates, and application engineering support.