1. Core characteristics

- Corrosion resistance barrier:

- Excellent performance in strong corrosive environments such as reducing acids (hydrochloric acid, sulfuric acid), oxidizing acids (nitric acid, mixed acid), chlorides, seawater, wet chlorine, sulfur-containing media (H₂S), especially resistant to corrosion in "oxidation-reduction mixed media" (such as hydrometallurgy, chemical reaction liquid);

- Inhibit pitting, crevice corrosion and stress corrosion cracking (SCC), and its corrosion resistance in chloride solutions far exceeds that of ordinary stainless steel (such as 316L).

- High temperature stability:

- Some grades (such as Hastelloy X) can resist oxidation at high temperatures of 1200℃, and most grades still maintain mechanical strength above 600℃, suitable for high temperature corrosion conditions (such as incinerators, flue gas treatment).

- Mechanical properties and processability:

- High strength (tensile strength ≥ 690 MPa), high toughness (elongation ≥ 40%), suitable for mechanical parts subject to high stress;

- Can be formed by hot rolling, cold drawing, precision processing, high surface finish (polishing/pickling treatment), good welding performance (need to match special welding wire).

2. Alloy system and typical grades

According to the alloy element ratio and performance focus, it is mainly divided into the following series (typical grades and characteristics):

1. B series (nickel-molybdenum alloy): Focus on reducing acid corrosion (such as hydrochloric acid)

- Hastelloy B-2 (UNS N10665): Resistant to hydrochloric acid at any temperature and concentration, outstanding performance in reduced sulfuric acid and phosphoric acid, often used in chemical reactor parts.

- Hastelloy B-3 (UNS N10675): Optimized thermal stability, better resistance to intergranular corrosion and pitting than B-2, more stable in high-temperature hydrochloric acid environment, and can withstand high temperatures above 900°C.

2. C series (nickel-chromium-molybdenum alloy): taking into account oxidation-reduction medium corrosion

- Hastelloy C-276 (UNS N10276): "all-round" alloy, resistant to wet chlorine, hypochlorite, chloride salt solution and mixed acid corrosion, commonly used in chemical reactors and desulfurization equipment, forging rods need to control the forging ratio ≥4:1.

- Hastelloy C-22 (UNS N06022): high chromium + molybdenum + tungsten ratio, stronger resistance to local corrosion (pitting, crevice corrosion), suitable for oxidizing media containing chloride ions (such as nitric acid + hydrochloric acid mixture).

- Hastelloy C-2000 (UNS N06200): adding copper (Cu), the corrosion resistance in sulfuric acid and hydrofluoric acid is improved, and it has both oxidation-reduction environment adaptability, and is often used in nuclear waste treatment equipment.

- Hastelloy C-4 (UNS N06455): high chromium content (14-18%), excellent resistance to intergranular corrosion in high temperature oxidizing environment, suitable for heat treatment furnace parts.

3. G series (high chromium nickel-based alloy): Focus on phosphoric acid and oxidizing media

- Hastelloy G-30 (UNS N06030): Chromium content reaches 30%, excellent corrosion resistance in wet phosphoric acid, nitric acid + hydrofluoric acid mixture, used for shafts and fasteners of phosphoric acid production equipment.

4. X series (high temperature oxidation resistant alloy)

- Hastelloy X (UNS N06002): Add cobalt (Co) and tungsten (W), anti-oxidation below 1200℃, and resistant to neutral/reducing atmosphere, used for aircraft engine parts and industrial furnace pipes.

5. Other special grades

- Hastelloy N (UNS N10003): Designed specifically for the nuclear industry, resistant to high temperature fluoride salt corrosion, used for nuclear reactor components.

3. Manufacturing process and specifications

- Production process:

- Seamless bars: formed by hot rolling or cold drawing, the tube blank is vacuum melted + electroslag remelted (to ensure purity), and the finished product needs annealing, pickling or polishing;

- Forged bars: hot forging process (initial forging temperature 1200-1250℃, final forging temperature ≥900℃), forging ratio ≥4:1, to ensure internal density and uniformity;

- Precision machining: turning, grinding and other secondary processing can be provided to meet the needs of high-precision mechanical parts.

- Specification range:

- Diameter: 3mm~300mm (1/8 inch~12 inches);

- Length: conventional 6m, 12m, or on-demand length (up to 18m);

- Surface treatment: polishing, pickling, bright treatment, special finish can be customized

4. Implementation standards and quality control

- International standards:

- Seamless bars: ASTM B574/ASME SB574;

- Forged bars: ASTM B564/ASME SB564;

- European standards: EN 2.4602 (C-22), EN 2.4819 (C-276), etc.

- Inspection points:

- Chemical composition analysis (strictly control the content of impurities such as C, Si, S);

- Mechanical properties test (tensile strength, yield strength, elongation);

- Corrosion test (such as ASTM G28 intergranular corrosion test, G48 pitting test);

- Flaw detection (ultrasonic flaw detection UT, penetration test PT).

5. Typical application scenarios

1. Chemical and petrochemical industry:

- Reactor stirring shaft, pump shaft, valve core (C-276, C-22);

- Fasteners for concentrated hydrochloric acid and sulfuric acid delivery systems (B-3).

2. Oil and gas:

- Drill pipes and casings for sulfur-containing oil and gas wells (C-276);

- Shaft components of seawater treatment equipment for offshore platforms (C-2000).

3. Environmental protection and energy:

- High-temperature corrosion-resistant nozzles and flue components of waste incinerators (X);

- Corrosion-resistant structural parts of nuclear waste treatment equipment (C-2000, N).

4. Aerospace:

- High-temperature components of engine combustion chambers, turbine sealing rings (X);

- High-temperature oxidation-resistant bolts (C-4).

VI. Selection Recommendations

- Reducing environment (hydrochloric acid, sulfuric acid): B series is preferred (B-3 is better than B-2);

- Oxidation-reduction mixed medium (mixed acid, wet chlorine): C series (C-276 is universal, C-22 is more resistant to local corrosion);

- High temperature oxidizing environment (flue gas, heat treatment furnace): X series;

- Phosphoric acid or strong oxidizing acid: G-30;

- Nuclear industry and fluoride medium: Hastelloy N.