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Material: Nickel 20, 201, 200, 31
Type: Round bar,Square bar,Hex bar,Flat bar
Tolerance: H7 H9 H10 H11
Surface: Black or Bright or Pickling white
Diameter: 5~500mm
Length: ≦12M or As Per Client's Requirements.
●Four distinct grades: Nickel 200 & 201 are commercially pure (≥99% Ni); Alloy 20 is a Nb-stabilized Ni-Fe-Cr sulphuric-acid specialist; Alloy 31 is a super-austenitic high-Mo/Cr master of mixed-acid and chloride environments.
●Nickel 200 (N02200): the general-purpose choice — tensile ≥380 MPa, ideal for caustic soda, food processing, and electronics up to 315 °C.
●Nickel 201 (N02201): the high-temperature variant of Nickel 200 — carbon ≤0.02 % prevents graphite embrittlement above 315 °C.
●Alloy 20 (N08020): 3–4 % Cu + 2–3 % Mo + Nb stabilisation — the benchmark for 50–95 % H₂SO₄ service; ASTM B473 bar standard.
●Alloy 31 (N08031): 6.0–7.0 % Mo + 26–28 % Cr + 0.20 % N → PREN ≥ 54, outperforming 6Mo super-austenitic grades in HCl and phosphoric acid.
●Bar forms: Round, Flat, Square, Hexagonal, and Wire Rod — diameters from 3 mm to 350 mm across hot-rolled, cold-drawn, forged, and centreless-ground routes.
●Key standards: ASTM B160 (Ni 200/201), ASTM B473 (Alloy 20), ASTM B649 / B625 (Alloy 31), ASME SB counterparts, NACE MR0175, DIN 17752, EN 10272.
●Dual-certifiable grades available (200/201 combined chemistry); full MTR per EN 10204 3.1 on all shipments.
Type | Round Bar Square Bar Hexagon Bar Flat Bar | ||
Surface | Black or Bright or Pickling white | ||
Standard | SUS, AISI, DIN | ||
Manufacture Technique | Hot Rolling, Cold-drawing | ||
Diameter | 5~500mm | ||
Length | ≦12M or As Per Client's Requirements. | ||
Diameter Tolerance | H7 H9 H10 H11 | ||
Material Grade | Nickel 20, 201, 31, 200 | ||
All four grades are produced in five principal bar forms — Round, Flat, Square, Hexagonal, and Wire Rod — across diameter or section sizes from 3 mm to 350 mm.
Bar Form | Cross-Section | Standard Size Range | Typical Applications |
Round Bar | Circular | 3 – 350 mm (diameter) | Pump shafts, valve stems, machined parts, fasteners |
Flat Bar | Rectangular | 3 – 150 mm (thickness) × up to 600 mm (width) | Structural supports, corrosion-resistant liners |
Square Bar | Square | 5 – 150 mm (side) | Key stock, structural frames, fabrication blanks |
Hexagonal Bar | Hexagon | 6 – 100 mm (across flats) | Bolts, studs, nuts, instrument fittings |
Wire Rod | Round (coiled) | 3 – 16 mm (diameter) | Cold-forming, fastener blanks, welding products |
Source: Standard commercial range. Custom lengths and sizes available to order.
All four grades are produced via vacuum-induction melting (VIM) followed by electro-slag remelting (ESR) for quality-critical applications. The standard commercial route is electric-arc (EAF) or AOD refining to achieve low sulphur and controlled nitrogen levels. Bars are produced by hot rolling, hot forging, cold drawing, or centreless grinding depending on diameter and tolerance requirements.
Hot Rolling
Ingot or continuous-cast billet is reheated to 1,000–1,200 °C and rolled to shape. Hot rolling is the most economical route for bar diameters of 20 mm and above. The resulting bar has an as-rolled or descaled surface. For Nickel 200/201, hot rolling produces coarse grain sizes; controlled rolling followed by annealing gives the ductile microstructure specified in ASTM B160.
Cold Drawing
A hot-rolled bar is drawn through progressively smaller dies at room temperature, improving dimensional accuracy (±0.05 mm typical), surface finish (Ra ≤ 1.6 µm), and tensile properties through work hardening. Intermediate annealing between passes retains ductility. Cold-drawn Alloy 20 bars comply with ASTM B473 and exhibit a brighter appearance critical for pharmaceutical and food-grade installations.
Forging
Open-die or closed-die forging converts ingots to near-net shapes for large-diameter (≥100 mm) bars and disc blanks. Forging refines the macrostructure, closes porosity, and aligns grain flow for maximum mechanical performance. Alloy 31 and Alloy 20 forged bars for valve and pump bodies are typically supplied per ASTM B462/B473 with full ultrasonic inspection.
Centreless Grinding
For the tightest dimensional tolerances (h6, IT6), centreless grinding removes the decarburised or oxidised surface layer and achieves roundness ≤ 0.010 mm. This is the preferred process for hydraulic actuator shafts and precision valve stems in Nickel 200/201 and Alloy 20.
Property | Nickel 200 | Nickel 201 | Alloy 20 | Alloy 31 |
UNS / W.Nr. | N02200 / 2.4060 | N02201 / 2.4068 | N08020 / 2.4660 | N08031 / 1.4562 |
Common Name | Nickel 200 | Nickel 201 | Alloy 20 / Carpenter 20 | Alloy 31 / VDM 31 |
Base System | Ni (≥99 %) | Ni (≥99 %, low C) | Ni-Fe-Cr-Cu-Mo (Nb stab.) | Ni-Fe-Cr-Mo-N-Cu |
Strengthening Mechanism | Solid solution | Solid solution | Solid solution + Nb stabilisation | Solid solution + N austenite stabiliser |
Key Alloying Feature | Commercially pure nickel | Ultra-low carbon (≤0.02 %) | Nb (Cb) IGC prevention; Cu for H₂SO₄ | High Mo + N: PREN ≥ 54 |
Primary Service Temp. | Up to 315 °C | 315 °C to 600 °C | -100 °C to 400 °C | -196 °C to 400 °C |
Primary Function | Caustic/alkali resistance; electronics; magnetics | High-temp caustic; salt evaporators | H₂SO₄ / H₃PO₄ / chemical process | Mixed acid / HCl / offshore / FGD |
Bar Standard | ASTM B160 | ASTM B160 | ASTM B473 | ASTM B649 |
Sources: ASTM B160/B473/B649; Special Metals Corp. technical bulletins; VDM Metals Alloy 31 datasheet.
Nickel 200/201 bars are primarily governed by ASTM B160 (and ASME SB-160); Alloy 20 bars by ASTM B473/B462; and Alloy 31 bars by ASTM B649 (solution-annealed bar/wire rod). All grades have corresponding ASME SB equivalents recognised under the ASME Boiler and Pressure Vessel Code. Sour-service applications additionally require compliance with NACE MR0175 / ISO 15156.
Standard | Product Form | UNS / Grade | Scope & Notes |
ASTM B160 | Bar & Rod (Ni 200 & 201) | N02200 / N02201 | Covers hot-rolled, cold-drawn, and forged round, square, hexagonal, and flat bar in commercially pure nickel |
ASME SB-160 | Bar & Rod (Ni 200 & 201) | N02200 / N02201 | ASME Boiler & Pressure Vessel Code equivalent of ASTM B160 |
ASTM B473 | Bar (Alloy 20) | N08020 | Covers hot-finished and cold-finished round, hex, square, and flat bar in Nb-stabilised austenitic alloy |
ASME SB-473 | Bar (Alloy 20) | N08020 | ASME equivalent of ASTM B473 |
ASTM B462 | Forged Fittings / Bar (Alloy 20) | N08020 | Flanges, fittings, and valve parts in forged Alloy 20; also covers bar billets for subsequent machining |
ASTM B649 | Bar & Wire Rod (Alloy 31) | N08031 | Hot- and cold-finished bar and wire rod in N08031 and related high-nickel austenitic alloys |
ASTM B625 | Sheet & Plate (Alloy 31) | N08031 | Includes Alloy 31 plate for cross-reference with bar product chemical composition |
EN 10272 | Bar (European standard) | N08031 / 1.4562 | European specification for austenitic stainless steel and nickel-alloy bar for pressure equipment |
DIN 17752 | Ni and Ni alloy bar | N02200 / N02201 | German counterpart for commercially pure nickel bar (superseded by EN, still referenced in older equipment specs) |
NACE MR0175 / ISO 15156 | Sour-service qualification | N08020 / N08031 | Defines hardness limits and conditions for use of nickel alloys in H₂S-containing oil & gas environments |
AMS 2700 | Passivation | All grades | Surface passivation requirements for nickel alloy components in aerospace and critical service |
EN 10204 3.1 | Material Test Report | All grades | Third-party inspection: chemical analysis + mechanical test results on heat/lot basis; required for pressure equipment |
Sources: ASTM International; ASME BPVC; NACE International (now AMPP); EN/DIN standards. Customer-specific standards (e.g., API, Lloyd's, DNV) available on request.
Table 5-A: Nickel 200 & Nickel 201 — Element Limits (wt %)
Element | Nickel 200 (N02200) | Nickel 201 (N02201) | Role / Significance |
Nickel (Ni) | ≥99.0 | ≥99.0 | Primary element; determines corrosion behaviour and magnetic properties |
Carbon (C) | ≤0.15 | ≤0.02 | KEY DIFFERENCE: Low C in Ni 201 prevents graphite precipitation above 315 °C |
Iron (Fe) | ≤0.40 | ≤0.40 | Residual; slight solid-solution strengthening effect |
Manganese (Mn) | ≤0.35 | ≤0.35 | Sulphur scavenger; improves hot workability |
Silicon (Si) | ≤0.35 | ≤0.35 | Residual deoxidant |
Copper (Cu) | ≤0.25 | ≤0.25 | Residual; enhances resistance to H₂SO₄ slightly |
Sulphur (S) | ≤0.010 | ≤0.010 | Controlled to minimise hot cracking during welding |
Source: ASTM B160 / Special Metals Corporation Nickel 200/201 Technical Bulletin.
Table 5-B: Alloy 20 & Alloy 31 — Element Limits (wt %)
Element | Alloy 20 (N08020) | Alloy 31 (N08031) | Role / Significance |
Nickel (Ni) | 32.0 – 38.0 | 30.0 – 32.0 | High Ni base → SCC immunity in chloride; Ni + Cu in A20 suppresses H₂SO₄ attack |
Chromium (Cr) | 19.0 – 21.0 | 26.0 – 28.0 | Passive film; high Cr in A31 dramatically raises PREN |
Iron (Fe) | Balance | Balance | Cost-reducing matrix element |
Molybdenum (Mo) | 2.0 – 3.0 | 6.0 – 7.0 | Pitting & crevice resistance; Mo is the primary driver of PREN difference |
Copper (Cu) | 3.0 – 4.0 | 1.0 – 1.4 | H₂SO₄ passivation in A20; moderate corrosion benefit in A31 |
Niobium/Cb (Nb) | ≥8×C, max 1.0 | — | Stabiliser in A20: ties up carbon to prevent intergranular corrosion at welds |
Nitrogen (N) | — | 0.15 – 0.25 | Austenite stabiliser in A31; direct PREN contributor (+16 × %N) |
Carbon (C) | ≤0.07 | ≤0.015 | Low C in A31 minimises chromium carbide precipitation |
Manganese (Mn) | ≤2.0 | ≤2.0 | Hot workability aid |
Silicon (Si) | ≤1.0 | ≤0.30 | Lower limit in A31 to maintain corrosion resistance in acids |
Sources: ASTM B473 (Alloy 20); ASTM B649 / EN 10272 (Alloy 31); VDM Metals Alloy 31 datasheet.
Nickel 200/201 annealed bars deliver moderate strength with exceptional ductility (elongation ≥ 40 %).
Alloy 20 annealed bars offer a tensile strength ≥ 552 MPa (80 ksi) with ≥ 30 % elongation.
Alloy 31 achieves tensile ≥ 650 MPa at elevated elongation ≥ 35 %, thanks to the nitrogen-enhanced austenite.
Grade | Condition | Tensile (MPa / ksi) | Yield (0.2 %) (MPa / ksi) | Elong. (%) | Hardness | Notes |
Nickel 200 (N02200) | Annealed (ASTM B160) | ≥380 (55) | ≥150 (22) | ≥40 | ≤80 HRB | Standard condition; suitable for most room- and moderate-temperature service |
Nickel 200 (N02200) | Cold-Drawn (hard) | 620–790 (90–115) | 480–620 (70–90) | ≥5 | 92–98 HRB | Work-hardened for shafts and fasteners requiring higher strength |
Nickel 201 (N02201) | Annealed (ASTM B160) | ≥345 (50) | ≥100 (15) | ≥40 | ≤75 HRB | Lower minimum due to reduced C; specify for service > 315 °C to avoid embrittlement |
Alloy 20 (N08020) | Annealed (ASTM B473) | ≥552 (80) | ≥241 (35) | ≥30 | ≤95 HRB | Single heat-treatment condition; balanced strength/ductility for acid-plant fabrication |
Alloy 31 (N08031) | Annealed (ASTM B649) | ≥650 (94) | ≥320 (46) | ≥35 | ≤95 HRB | High Cr + Mo + N; strength maintained across broad temperature range |
Alloy 31 (N08031) | Annealed (EN 10272) | 650 – 900 (94–130) | ≥300 (44) | ≥35 | — | European specification; slightly broader tensile range than ASTM B649 |
Sources: ASTM B160/B473/B649; Special Metals Corp. bulletins; VDM Metals; EN 10272. All values minimum unless noted.
Grade selection follows a service-environment hierarchy:
(1) if the medium is caustic alkali or dry HF → Nickel 200/201;
(2) if service is above 315 °C with caustic → Nickel 201;
(3) if the medium is sulfuric acid (broad concentration) → Alloy 20;
(4) if chloride pitting, phosphoric acid with impurities, or mixed-acid FGD scrubbing → Alloy 31.
Application / Service Environment | Recommended Grade | Selection Rationale |
Caustic Soda (NaOH) Evaporators & Storage | Nickel 201 | Nickel 200 prone to graphite embrittlement > 315 °C; Ni 201 preferred for high-temp / high-conc. caustic |
Sulfuric Acid Plants (H₂SO₄ 10–95 %) | Alloy 20 | Cu + Mo target the H₂SO₄ passivation window; Nb stabilisation prevents IGC at welds; industry-proven in absorbers, coolers, piping |
Phosphoric Acid Production (wet-process H₃PO₄) | Alloy 31 | H₃PO₄ is contaminated with HF and Cl⁻ — Alloy 31 handles both; replaces nickel alloys at lower cost per corrosion unit |
Flue Gas Desulfurisation (FGD) Scrubbers & Absorbers | Alloy 31 | Aggressive mix of H₂SO₄, HCl, HF, and chlorides at elevated temperatures; PREN ≥ 54 prevents pitting failure |
Food Processing & Pharmaceutical Equipment | Nickel 200 / 201 | Inert in food-contact media; low Fe avoids product contamination; FDA/EC 1935/2004 compliant |
Anhydrous Hydrofluoric Acid (HF) Handling | Nickel 200 | Unique passivity of pure Ni in dry/anhydrous HF — stainless steels corrode rapidly in this medium |
Electroplating & Electronics Components | Nickel 200 | Magnetic properties, high electrical conductivity, and high purity critical for anodes, bus bars, electrode supports |
Offshore / Subsea Pump Shafts & Valve Stems | Alloy 31 | Chloride + H₂S service; PREN ≥ 54 exceeds seawater CPT requirement; NACE MR0175 compliant hardness achievable |
Chemical Reactor Components (Multi-Acid Service) | Alloy 20 | Broad acid resistance with proven 60+ year track record in mixed H₂SO₄/HNO₃ and phosphate fertiliser environments |
Salt Evaporation & Chlor-Alkali Processes | Nickel 200 / 201 | Exceptional resistance to brine and chlorinated caustic; corrosion rates < 0.025 mm/yr in saturated NaCl + NaOH |
Cryogenic Service (LNG, -196 °C) | Alloy 31 / Alloy 20 | Both retain full ductility and toughness at cryogenic temperatures due to stable austenitic FCC structure |
Sources: Special Metals Corp.; VDM Metals; ASM Handbook Vol. 13B; Corrosion Materials Engineering (Schweitzer); ASTM G48 CPT data.
Q1: What is the difference between Nickel 200 and Nickel 201?
The sole compositional difference is carbon content. Nickel 200 permits up to 0.15 % carbon, while Nickel 201 restricts carbon to 0.02 % maximum. Above 315 °C (600 °F), the carbon in Nickel 200 can precipitate as graphite at grain boundaries, causing significant embrittlement. Nickel 201 is therefore mandatory for elevated-temperature applications such as caustic-soda evaporators, chlor-alkali cells, and any service where the metal temperature exceeds 315 °C continuously.
Q2: Why is Alloy 20 the standard choice for sulfuric acid service?
Alloy 20 was specifically developed to resist sulfuric acid across a broad concentration range (0–95 %) and up to moderate temperatures (50–70 °C). Its copper addition (3–4 %) combines with nickel to extend the passive range in H₂SO₄; molybdenum (2–3 %) enhances pitting resistance; and niobium (Cb) stabilisation (≥8 × carbon) ties up carbon to prevent intergranular corrosion in welded joints. No standard stainless steel can match this combination in mixed-acid or H₂SO₄-dominated environments.
Q3: What does PREN ≥ 54 mean for Alloy 31, and why does it matter?
The Pitting Resistance Equivalent Number (PREN = %Cr + 3.3 × %Mo + 16 × %N) is a predictive index for resistance to chloride pitting. Alloy 31 achieves PREN ≈ 27 + (3.3 × 6.5) + (16 × 0.2) ≈ 52–54, compared to approximately 42–44 for standard 6Mo grades (254 SMO, AL-6XN) and 25–26 for 316L. In practice, Alloy 31 maintains a Critical Pitting Temperature (CPT) > 60 °C in chloride media, making it suitable for seawater-cooled equipment, offshore structures, and desalination components where pitting is the predominant failure mode.
Q4: Can Nickel 200 be used in hydrofluoric acid (HF) service?
Yes — anhydrous or near-anhydrous hydrofluoric acid is one of the few environments where commercially pure nickel (Nickel 200/201) is uniquely suitable. Pure nickel forms a resistant nickel-fluoride film in dry HF. Stainless steels, carbon steels, and most copper alloys corrode rapidly under these conditions. However, wet or aqueous HF (where fluoride ions are in solution) requires careful evaluation; in that case, Monel 400 or Inconel 625 may be preferred.
Q5: What are the bar size ranges typically available for each grade?
For Nickel 200/201, standard round bar diameters range from 3 mm to approximately 250 mm (cold-drawn up to ~100 mm; hot-rolled and forged for larger sizes). Alloy 20 round bar is available from approximately 6 mm to 300 mm diameter. Alloy 31 round bar is produced in diameters from approximately 10 mm to 350 mm, with forged bar most common above 150 mm. Custom sizes and extra-length bars are available against order from qualified mills.
Q6: Are Nickel 200 and Nickel 201 magnetic?
Yes. Commercially pure nickel is ferromagnetic at room temperature — Nickel 200/201 are distinctly magnetic, unlike austenitic stainless steels. This property is exploited in electroplating anodes, magnetostrictive transducers, and electrical and electronic components. In environments where magnetism is undesirable (e.g., MRI equipment surroundings or certain naval applications), Alloy 20 or Alloy 31 (both non-magnetic austenitic alloys) should be specified instead.
Q7: Which grade is best for phosphoric acid with chloride and fluoride impurities?
Alloy 31 (N08031). Wet-process phosphoric acid produced from phosphate rock contains significant chloride (up to 1,000 ppm) and fluoride impurities that degrade the corrosion resistance of Alloy 20, standard stainless steels, and even Hastelloy C-276 in some conditions. Alloy 31's combination of high Mo (6–7 %), high Cr (26–28 %), and nitrogen is specifically proven in phosphoric acid concentrators, holding tanks, and agitators. It has progressively replaced nickel alloys in phosphate fertiliser plants at significantly lower material cost.
Q8: What welding consumables are recommended for these grades?
Nickel 200/201: AWS ERNi-1 (filler) / ENi-1 (electrode); note Nickel 200 should not be welded if service will be >315 °C — specify Nickel 201 base metal and matching filler. Alloy 20: AWS ERNiCrMo-3 (Inconel 625 filler) provides slight over-alloying for dilution-resistant welds; some specifications permit matching Alloy 20 filler (AWS ENiCrFe-6). Alloy 31: AWS ERNiCrMo-13 (matching VDM FM 31) or AWS ERNiCrMo-3 (Inconel 625) for conservative applications. All welded joints in Alloy 20 and Alloy 31 must be solution-annealed if the full corrosion resistance is required after fabrication.
