Hastelloy B
Complete analysis of Hastelloy B alloy (UNS N10001)
I. Implementation standards (classified by product form)
The technical specifications of Hastelloy B cover American standards (ASTM/ASME), national standards and international standards, targeting different product forms:
- Forgings: ASTM B564 (American standard, specifying the chemical composition, heat treatment and mechanical properties of forgings);
- Plates/strips: ASTM B435 (or extended with reference to ASTM B575, focusing on the processability of heavy plates);
- Bars/wires: ASTM B434 (specifications for the dimensions and performance of bars and wires);
- National standard equivalent: GB/T 15007 grade NS321 (Chinese corrosion – resistant alloy system, equivalent to Hastelloy B);
- International extension: European standard EN 10269 (general standard for corrosion – resistant alloy bars).
II. Name and Code
- General name: Hastelloy B;
- Authoritative identification:
- American standard: UNS N10001 (core number, unique general identifier);
- National standard: NS321 (Chinese corrosion – resistant alloy grade);
- European standard: W.Nr. 2.4617 (Germany), NiMo28Fe (component abbreviation, highlighting high Mo content);
- Commercial alias: Hastelloy B – 1 (early grade, the current mainstream is the optimized B series basic type).
III. Chemical composition (mass fraction,%, typical range of ASTM standard)
Hastelloy B is a nickel – molybdenum – based corrosion – resistant alloy, which resists strong reducing corrosion through the synergy of “high Mo + low Cr/Fe”. Its composition is as follows:
| Element | Content Range | Core Function |
|---|---|---|
| Nickel (Ni) | Balance (≈62 – 68) | Stabilizes the austenitic matrix and resists stress corrosion |
| Molybdenum (Mo) | 26.0 – 30.0 | Resists reducing media (hydrochloric acid, sulfuric acid) and inhibits pitting corrosion |
| Iron (Fe) | 4.0 – 6.0 | Reduces cost and assists in strengthening |
| Chromium (Cr) | ≤1.0 | Slightly improves oxidation resistance and controls the precipitation of β phase (Ni₄Mo) |
| Cobalt (Co) | ≤2.5 | Impurity control (residual element, limiting the risk of hot cracking) |
| Manganese (Mn) | ≤1.0 | Improves hot working fluidity |
| Silicon (Si) | ≤1.0 | Optimizes casting structure and inhibits impurities |
| Carbon (C) | ≤0.05 | Avoids carbide precipitation and prevents intergranular corrosion |
| Vanadium (V) | 0.2 – 0.4 | Refines grains and assists in strengthening (trace amount) |
| Phosphorus (P) | ≤0.04 | Inhibits cold brittleness |
| Sulfur (S) | ≤0.03 | Inhibits hot working cracks |
IV. Mechanical properties (solid solution treatment state, typical value at room temperature)
After solution treatment (water quenching at 1050 – 1150°C), Hastelloy B combines medium – high strength and high plasticity, and can be stably used at -200 – 400°C:
| Performance Indicator | Typical Value (Solution State) | Remarks |
|---|---|---|
| Tensile Strength | ≥690 MPa | Can be improved by cold working (e.g., reaches 800 MPa + after cold rolling) |
| Yield Strength (0.2%) | ≥310 MPa | Some standards require ≥345 MPa |
| Elongation (%) | ≥40 | Excellent formability, supporting rolling and welding |
| Hardness (HB) | 100 – 230 | Soft state, convenient for processing |
V. Heat Treatment Requirements
- Core Process: Solution Treatment
- Temperature: 1050 – 1150°C (hold for 1 – 2 hours to ensure uniform solid solution of Mo and inhibit the precipitation of β phase Ni₄Mo);
- Cooling: Water quenching or rapid air cooling (to prevent the precipitation of harmful phases and ensure corrosion resistance).
- Processing Auxiliary Points:
- Hot working: Temperature range 1100 – 1200°C (quickly pass through the 700 – 870°C sensitization zone to avoid embrittlement caused by the precipitation of β phase);
- Cold working: Easy to form in the solution state, single deformation amount ≤30% (excessive cold working requires intermediate annealing at 1050°C to restore plasticity).
VI. Main application fields
Hastelloy B, due to its “resistance to reducing corrosion (hydrochloric acid, sulfuric acid) + medium – temperature stability”, focuses on extreme reducing environments:
- Chemical Industry:
- Hydrochloric acid production: Evaporators, heat exchangers (resistant to concentrated hydrochloric acid and hot hydrochloric acid corrosion at ≤100°C, tests show annual corrosion rate < 0.1mm);
- Sulfuric acid/phosphoric acid devices: (under medium – concentration, non – oxidizing conditions, such as dilute sulfuric acid at ≤80°C, formic acid/acetic acid media).
- Oil and Natural Gas:
- Acid gas fields: (containing H₂S reducing medium, resistant to sulfur corrosion), crude oil desulfurization towers (resistant to acid liquid corrosion).
- Environmental Protection and Energy:
- Hydrometallurgy: Leaching tanks, pipelines (resistant to acid leaching liquid (such as hydrochloric acid leaching) corrosion);
- Nuclear industry: High – purity acid treatment systems (resistant to strong reducing media, such as nuclear waste dissolution tanks).
- Special Scenarios:
- Chloride reducing environment: (resistant to Cl⁻ stress corrosion cracking, such as salt water desalination pretreatment equipment).
Supplementary Characteristics
- Corrosion resistance limit: Not resistant to strong oxidizing media (such as concentrated nitric acid, chromic acid) and mixed acids containing strong oxidants (such as nitric acid + hydrochloric acid);
- Weldability: ERNiMo – 3 welding wire (AWS A5.14) is recommended, and heat input should be controlled (≤1.5kJ/mm) to avoid hot cracking. The corrosion resistance of the welded state is consistent with that of the base metal;
- Differences from B – 2/B – 3:
- Hastelloy B – 2: Reduces C (≤0.02%) and Si (≤0.2%), improving intergranular corrosion resistance;
- Hastelloy B – 3: Optimizes Cr (1 – 3%) and Fe (1 – 3%), expands the temperature resistance to ≤500°C, and has stronger resistance to sulfuric acid/phosphoric acid.
Hastelloy B is a “benchmark alloy for strong reducing corrosion”, and its core competitiveness is high Mo resistance to hydrochloric acid/sulfuric acid. When selecting materials, it is necessary to match standards (such as B – 2/B – 3 for harsher environments) based on medium reducibility, temperature, and processing state.