High-Chromium Ni-Cr-Fe-Mo-Cu Alloy for Wet-Process Phosphoric Acid and Oxidizing Environments | ASTM B582 | Special Alloys

UNS NUMBER N06030

ALLOY FAMILY Ni-Cr-Fe-Mo-Cu

HARDENING Solid Solution

UTS (MIN) ≥586 MPa

MAX TEMP ~1000°C

DENSITY 8.22 g/cm³

1. Overview — Why G-30 Was Developed

Hastelloy G-30 (UNS N06030) carries 28.0–31.5% chromium — nearly double C-276 and the highest Cr content of any alloy in the Hastelloy family. This composition was developed specifically for wet-process phosphoric acid (WPA) production, where digestion of phosphate rock exposes equipment to a uniquely aggressive cocktail of fluoride, chloride, sulfate, and silica contaminants at temperatures up to 120°C.

Beyond WPA, G-30's high-Cr chemistry makes it a strong performer in concentrated nitric acid (HNO₃) and HNO₃/HF pickling mixtures used in nuclear fuel reprocessing. The combination of high Cr, moderate Mo (4–6%), W (1.5–4%), and Cu (1–2.4%) gives it a corrosion profile that bridges oxidizing and mildly reducing environments — but its true calling card is WPA service, where it has been the industry standard alloy for over three decades.

2. Chemical Composition (Weight %)

Composition per ASTM B582 / B581. Starred elements (⭐) are the high-Cr specialist signature. Cr at 28–31.5% is the defining feature of G-30.

Element	Min	Max	Role in Alloy
Nickel (Ni)	Balance	—	Austenitic matrix; resists caustic & chloride SCC
Chromium (Cr) ⭐	28.0	31.5	HIGHEST in Hastelloy family. Forms Cr₂O₃ passive film; resists HNO₃, F⁻, oxidizing acids
Iron (Fe)	13.0	17.0	Cost-effective matrix strengthener; aids weldability
Molybdenum (Mo)	4.0	6.0	Resists pitting/crevice in chloride + fluoride service
Tungsten (W) ⭐	1.5	4.0	Strengthens passive film in reducing conditions; boosts pitting resistance
Copper (Cu) ⭐	1.0	2.4	Improves resistance to H₂SO₄; passivates in mixed-acid environments
Niobium (Nb)	0.30	1.5	Stabilizer — ties up C, prevents carbide precipitation at grain boundaries
Cobalt (Co)	—	5.0	Residual — controlled to minimize in nuclear applications
Manganese (Mn)	—	1.5	Deoxidizer; aids weldability
Silicon (Si)	—	0.80	Deoxidizer; kept low to avoid HNO₃ attack
Carbon (C)	—	0.03	Ultra-low C minimizes grain-boundary carbide precipitation

⭐ Signature element for G-30's high-Cr specialty. Cr at 28–31.5% is what distinguishes G-30 from every other Hastelloy grade.

3. Mechanical Properties (Solution-Annealed)

Mechanical properties per ASTM B582 at room temperature. G-30 is a solid-solution-strengthened alloy — not age hardenable.

Property	Value (Min / Typical)	Notes
Ultimate Tensile Strength (UTS)	≥586 MPa (typical ~690)	Lower than C-276 due to higher Fe/Cr solid-solution balance
Yield Strength (0.2% offset)	≥240 MPa (typical ~310)	Adequate for most pressure-vessel service
Elongation (in 2″ / 50mm)	≥30%	Excellent formability for dished heads, cone reducers
Hardness	≤100 HRB (typical 85–95)	Soft condition — easily machined and formed
Elastic Modulus (E)	197 GPa	Pressure-vessel design parameter

3.1 Elastic Constants

Constant	Value
Young's Modulus (E)	197 GPa
Shear Modulus (G)	76 GPa
Poisson's Ratio (ν)	0.30

4. Physical Properties

Property	Value
Density	8.22 g/cm³
Melting Range	1330–1380°C
Thermal Conductivity (at 20°C)	10.2 W/m·K
Specific Heat (0–100°C)	440 J/kg·K
Electrical Resistivity (20°C)	1.17 μΩ·m
CTE (20–100°C)	12.3 ×10⁻⁶/K
CTE (20–300°C)	14.2 ×10⁻⁶/K

5. Heat Treatment & Fabrication

G-30's 28–31.5% Cr content makes it more susceptible than C-276 to sigma (σ) phase precipitation during slow cooling through 600–900°C. Heat treatment procedure must be followed precisely.

Step 1 — Solution Anneal

Heat to 1177°C (2150°F), hold for sufficient time (typically 30 min per inch of thickness, minimum 15 min), then water quench rapidly. Rapid quench is critical to prevent σ-phase and maintain optimum corrosion resistance.

Step 2 — Stress Relief (if required)

400–500°C (750–930°F) for 1–2 hours followed by air cool. Use only when full solution anneal is not feasible; stress relief at higher temperatures risks sensitization.

Step 3 — Post-Weld Heat Treatment (PWHT)

Recommended for critical WPA service. Solution anneal welded fabrications at 1177°C followed by rapid water quench. For sections >25mm thick, water quench with agitation is required to avoid sensitization in the heat-affected zone (HAZ).

Fabrication Notes

Hot working: 950–1175°C; finish above 900°C; cool rapidly.
Cold working: Readily formable in annealed condition (≤100 HRB). Work-harden rate moderate.
Welding: GTAW (TIG) preferred with ERNiCrMo-11 filler (matching composition). Avoid high heat input. PWHT strongly recommended.
Machining: Use rigid tooling, positive feeds, sharp carbide inserts. Coolant essential. Workpiece will gummy if tools are dull.

6. Corrosion Resistance

G-30 is specialized for oxidizing acids and wet-process phosphoric acid (WPA) — environments where the high Cr content (28–31.5%) builds a thick, fluoride-resistant Cr₂O₃ passive film. It is not a general-purpose reducing-acid alloy (use C-276 or B-3 for those).

Environment	Rating	Typical Rate	Notes
WPA ⭐ 54% P₂O₅, 120°C, F⁻/Cl⁻/H₂SO₄ contaminants	★★★★★	<0.10 mm/yr	Industry standard for WPA evaporators, agitators, piping. Outperforms all 300-series SS and most Ni-Cr-Mo alloys.
HNO₃ (all concentrations) to boiling	★★★★★	<0.05 mm/yr	Excellent — among the best commercial alloys for hot concentrated HNO₃
HNO₃ / HF mixtures nuclear dissolver service	★★★★★	<0.15 mm/yr	Used in nuclear fuel reprocessing dissolvers. High Cr resists F⁻ attack.
H₂SO₄ (dilute) with oxidizing impurities	★★★★	<0.50 mm/yr	Cu content provides passivation. Best for H₂SO₄ containing oxidizers (HNO₃, Fe³⁺).
HCl (any concentration)	★★	>0.80 mm/yr	Fair to moderate. NOT recommended for HCl service. Mo content too low (4–6%).
Pitting / Crevice PREN ≈ 44–57	★★★★	—	Good. PREN 44–57 adequate for WPA contaminant service. For high-Cl⁻ service consider C-22 or C-276.

7. Grade Selection — Where G-30 Fits

Application	Suitability	Cost Index	Why G-30
Wet-Process Phosphoric Acid (WPA)	★★★★★	$$$$	The defining application. Industry standard for 30+ years.
Hot Concentrated HNO₃	★★★★★	$$$$	High Cr gives superior nitric acid resistance over C-276.
Nuclear HNO₃/HF Dissolvers	★★★★	$$$$	Co ≤5% controlled; used in spent-fuel reprocessing.
H₂SO₄ with Oxidizing Impurities	★★★★	$$$$	Cu passivation helps. Best when oxidizers are present.
HCl Service (any)	★★	N/A	Not recommended. Use B-3, C-276, or C-2000.

Selection verdict: G-30 is the WPA and oxidizing-acid specialist. Choose G-30 when the service is wet-process phosphoric acid (any concentration), hot HNO₃, or HNO₃/HF mixtures. For reducing acids (HCl, HF alone, H₂SO₄ pure) use C-276, B-3, or C-2000 instead.

8. Typical Applications

Industry	Equipment / Components	Service Environment
Phosphoric Acid (Fertilizer)	WPA evaporators, agitator shafts, tank coils, piping, heat exchangers, pump casings	54% P₂O₅ + F⁻/Cl⁻/H₂SO₄/SiO₂ at 100–120°C
Fertilizer Production	DAP/MAP reactor agitators, phosphoric acid concentrators, scrubber internals	Hot phosphoric acid with gypsum slurry
Nuclear Fuel Reprocessing	Spent-fuel dissolvers, HNO₃ evaporators, off-gas scrubbers	HNO₃ / HF mixtures with radioactive species
Chemical Processing	HNO₃ stripper columns, pickling tanks, oxidizer loop piping	Hot concentrated HNO₃; H₂SO₄ with HNO₃

9. Project Case Study — North African Phosphate Fertilizer

10. Standards & Equivalents

Standard	Title / Form
UNS N06030	Unified Numbering System designation
ASTM B582	Plate, Sheet, and Strip — primary product spec
ASTM B581	Rod, Bar, and Wire
ASTM B619 / B622 / B626	Welded / Seamless / Welded Tube — pipe & tubing
ASTM B366	Factory-Made Wrought Fittings (e.g., WP-G30)
DIN 2.4603	German / European Werkstoff number (NiCr30FeMo)

11. Frequently Asked Questions

12. Related Resources

13. Request a Quote

HT PIPE supplies ASTM B582 plate, B581 bar, B619/B622/B626 pipe, and B366 fittings in UNS N06030 — all with EN 10204 3.1 certification. For WPA, HNO₃, or nuclear service applications, contact our special-alloys team with your spec and we will respond within 24 hours.