Hastelloy C-4 – UNS N06455
Nickel-chromium-molybdenum alloy with high thermal stability
Ni-Cr-Mo alloy (16Cr-16Mo) with very low C and Si, stabilized with Ti and free of tungsten. This keeps it stable even after exposure to 650 – 1,040 °C: intergranular corrosion in the HAZ is minimal and ductility is retained, even in welded parts without PWHT. Corrosion resistance similar to C276 in reducing and oxidizing chloride media.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | N06455 |
| W.Nr./EN | 2.4610 – NiMo16Cr16Ti |
| DIN | NiMo16Cr16Ti |
| JIS | NW6455 |
| Trade names | Hastelloy C-4 (Haynes), Nicrofer 6616 hMo (VDM), Alloy C4 |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM B574 |
| Forging | ASTM B574 (forged bar); B564 does not cover N06455 |
| Plate | ASTM B575 |
| Tube | ASTM B622 (seamless), B619/B626 (welded) |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7505.12.10 | 7505.12 | 7505.12.3000 | 7505 12 00 |
| Hot-rolled bar | 7505.12.10 | 7505.12 | 7505.12.3000 | 7505 12 00 |
| Plate (> 10 mm, width ≥ 600 mm) | 7506.20.00 | 7506.20 | 7506.20.3000 | 7506 20 00 |
| Seamless pipe | 7507.12.00 | 7507.12 | 7507.12.0000 | 7507 12 00 |
| Welded pipe | 7507.12.00 | 7507.12 | 7507.12.0000 | 7507 12 00 |
| Flange and fitting | 7507.20.00 | 7507.20 | 7507.20.0000 | 7507 20 00 |
Tariff class: nickel alloy (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM B574 / B575 (UNS N06455)
| Element | Range (%) |
|---|---|
| Ni | balance (≈ 65) |
| Cr | 14.0 – 18.0 |
| Mo | 14.0 – 17.0 |
| Fe | ≤ 3.0 |
| Co | ≤ 2.0 |
| Ti | ≤ 0.70 |
| Mn | ≤ 1.0 |
| Si | ≤ 0.08 |
| C | ≤ 0.015 |
| P | ≤ 0.04 |
| S | ≤ 0.03 |
Mechanical properties
solution annealed (ASTM B574)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 276 MPa |
| Tensile strength | ≥ 690 MPa |
| Elongation | ≥ 40% |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.64 g/cm³ |
| Melting range | 1,335 – 1,380 °C |
| Modulus of elasticity | 211 GPa (typical) |
| Thermal conductivity (20 °C) | 10.1 W/m·K |
| Thermal expansion (20–100 °C) | 10.8 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | An alloy for aqueous corrosion. Its strength is keeping ductility and corrosion resistance after thermal exposure between 650 and 1,040 °C, not structural use at high temperature. |
| Heat treatment | Solution annealing at ≈ 1,065 °C with rapid cooling (water). Normally used as welded, without PWHT. |
| Welding | Good weldability. Consumables: AWS A5.14 ERNiCrMo-7 and AWS A5.11 ENiCrMo-7. Low heat input and interpass ≤ 100 °C (typical). |
| Machining | Difficult, like the other Ni-Cr-Mo alloys: carbide, low speed and abundant coolant. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Reactors, exchangers and columns with chloride-contaminated acids
- Pickling and acid regeneration
- Flue gas desulfurization (FGD)
- Pulp and paper bleaching
- Pharmaceutical and agrochemical industry
- Waste and effluent treatment
Alternatives: C276 in strongly reducing media, with greater availability; C22 or 59 when strong oxidizers are present.
Hastelloy C-4: complete guide
What Hastelloy C-4 is
Hastelloy C-4 belongs to the family of nickel alloys, in the nickel-chromium-molybdenum group. Compared with C-276, it eliminates tungsten and limits iron to 3% max., which gives it thermal stability: it can be heated between 650 and 1,040 °C, for example when welding thick sections, without precipitating the phases that reduce corrosion resistance.
Mechanical properties
Solution annealed, ASTM B574 requires a minimum yield strength of 276 MPa, minimum tensile strength of 690 MPa and minimum elongation of 40%. The alloy is not hardenable by heat treatment.
Corrosion and limits of use
Resistance is similar to C-276 in dilute hydrochloric and sulfuric acid, chlorides, wet chlorine, organic acids and mixtures, with immunity to pitting, crevice corrosion and chloride stress corrosion cracking. In strongly oxidizing media C-22 is superior, and in hot concentrated hydrochloric acid B-2. It is an aqueous-corrosion alloy, used under the ASME code up to about 425 °C.
Applications
Welded reactors, exchangers, columns and piping in the chemical and pharmaceutical industry, chlor-alkali and wet chlorine process equipment, valve and pump components in chlorides, and pollution control equipment where the weld cannot be heat treated.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, solution annealing or annealing in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of Hastelloy C-4?
Per ASTM B574 / B575 (UNS N06455): Ni balance (≈ 65); Cr 14.0 – 18.0; Mo 14.0 – 17.0; Fe ≤ 3.0; Co ≤ 2.0; Ti ≤ 0.70.
Which standards cover Hastelloy C-4?
Bar: ASTM B574. Forging: ASTM B574 (forged bar); B564 does not cover N06455. Plate: ASTM B575. Tube: ASTM B622 (seamless), B619/B626 (welded).
Up to what temperature can Hastelloy C-4 be used?
An alloy for aqueous corrosion. Its strength is keeping ductility and corrosion resistance after thermal exposure between 650 and 1,040 °C, not structural use at high temperature.
Which materials can replace Hastelloy C-4?
C276 in strongly reducing media, with greater availability; C22 or 59 when strong oxidizers are present.
