# UNS N10629 Forgings: Alloy B-4 (2.4600) Rings, Flanges, Bars and Discs

**Source:** https://www.steelforgepieces.com/Nickel-Alloy/UNS-N10629.html
**Supplier:** Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
**Address:** No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
**Phone / WhatsApp / WeChat:** +86-189-2135-9659
**Email:** sales@steelforgepieces.com
**Last updated:** 1 September 2026

UNS N10629 is a wrought nickel-molybdenum alloy with 26 to 30% molybdenum and 65 to 72% nickel, sold as Alloy B-4 or Hastelloy B-4 and listed in Europe as W.-Nr. 2.4600 (NiMo28Fe4Cr). It resists hydrochloric acid at every concentration and temperature, along with sulfuric, phosphoric and acetic acid and other reducing media. Jiangyin Jiangnan Metal Co., Ltd. forges UNS N10629 into seamless rolled rings, flanges, shafts, round bars, discs, sleeves, bushings and tube sheets to ASTM B462 and ASTM B564, supplied solution annealed with EN 10204 3.1 or 3.2 certification.

| Identity | |
|---|---|
| UNS number | N10629 |
| Common name | Alloy B-4 / Hastelloy B-4 |
| Werkstoff number | 2.4600 |
| EN designation | NiMo28Fe4Cr |
| Alloy family | Nickel-molybdenum, Ni-28Mo |
| Forging standards | ASTM B462, ASTM B564 |
| Delivery condition | Solution annealed, quenched |
| Certification | EN 10204 3.1 / 3.2 |

## Grade overview

The nickel-molybdenum grades start with Alloy B (UNS N10001) and Alloy B-2 (UNS N10665). Both handle hydrochloric acid well, but B-2 is sensitive to beta phase precipitation. It can crack during hot working, and it can suffer attack in the heat affected zone of a weld. UNS N10629 keeps the same Ni-28Mo base, holds the composition tighter, and adds 0.5 to 1.5% chromium and 0.1 to 0.5% aluminum for thermal stability.

In the forge shop the difference shows up as a wider working window. The alloy still needs frequent reheats, a finish temperature above about 950 °C and a hard quench out of the solution anneal, but it takes upsetting and ring rolling better than B-2 does.

## Designations and equivalents

| System | Designation |
|---|---|
| UNS | N10629 |
| Trade and common names | Alloy B-4, Hastelloy B-4, Nimofer 6629 |
| Werkstoff (W.-Nr.) | 2.4600 |
| EN chemical symbol | NiMo28Fe4Cr |
| Forgings, flanges, valve parts | ASTM B462, ASTM B564 (ASME SB-462, SB-564) |
| Bar and rod | ASTM B335 |
| Plate, sheet, strip | ASTM B333 |
| Pipe and tube | ASTM B622 seamless; ASTM B619 and B626 welded |

Hastelloy is a registered trademark of Haynes International. Material supplied by Jiangyin Jiangnan Metal is made to UNS N10629 chemistry and to the standards listed above. It is not trademarked material.

## Chemical composition

Weight %. Nickel is the balance.

| Element | Ni | Mo | Fe | Cr | Co | Al | Mn | Cu | Si | C | P | S |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| wt % | Bal. 65 to 72 | 26.0 to 30.0 | 2.0 to 6.0 | 0.50 to 1.5 | 2.5 max | 0.10 to 0.50 | 1.5 max | 0.5 max | 0.05 max | 0.010 max | 0.02 max | 0.010 max |

Ranges are those permitted by the applicable product standards. The heat analysis and the product analysis of each piece are reported on the EN 10204 certificate that ships with the forging.

## Mechanical properties

Typical room temperature values in the solution annealed condition.

| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, Rm | 860 to 880 MPa | 125 to 128 ksi |
| Yield strength, Rp0.2 | 400 to 440 MPa | 58 to 64 ksi |
| Elongation at break, A5 | 45 to 57% | 45 to 57% |
| Fatigue strength | approx. 340 MPa | approx. 49 ksi |
| Shear strength | approx. 600 MPa | approx. 87 ksi |
| Hardness | approx. 88 HRB | approx. 88 HRB |

Acceptance minimums are those of the governing standard, for example ASTM B462 or ASTM B564, or of the customer specification, and are verified on test coupons taken from the forging.

## Physical properties

| Property | Value |
|---|---|
| Density | 9.2 g/cm3 (0.333 lb/in3) |
| Melting range | 1560 to 1610 °C (2830 to 2930 °F) |
| Elastic modulus | 220 GPa (32 x 10^6 psi) |
| Shear modulus | 83 GPa |
| Poisson's ratio | 0.31 |
| Coefficient of thermal expansion | approx. 10 µm/m·K |
| Specific heat capacity | 390 J/kg·K |
| Maximum mechanical service temperature | approx. 910 °C (1660 °F) |

## Corrosion resistance

UNS N10629 is a reducing service alloy. The main duty is hydrochloric acid at all concentrations up to the boiling point. It also holds up in sulfuric, phosphoric, acetic, formic and hydrobromic acid, and in chloride bearing reducing media, where it resists stress corrosion cracking, pitting and crevice attack.

**Not for oxidizing service.** Nitric acid, ferric and cupric ions, dissolved oxygen and other oxidizing contaminants attack nickel-molybdenum alloys quickly. Even a small carry-over of ferric chloride into an HCl stream will change the corrosion rate by orders of magnitude. Where the process moves between oxidizing and reducing conditions, specify a Ni-Cr-Mo grade such as Hastelloy C-276 or Hastelloy C-22.

## Manufacturing route

**Melting and raw material.** Billet is made to UNS N10629 chemistry by an EAF plus AOD or VOD route with electroslag remelting. ESR keeps sulfur and phosphorus low and gives the clean, even structure this alloy family needs. Heat numbers are carried from billet through to the finished piece and printed on the certificate.

**Open-die forging and ring rolling.** Billets are soaked and forged from 1150 to 1180 °C with frequent reheats, finishing above 950 °C to stay clear of the precipitation range. Rings are pierced and rolled on a radial-axial ring rolling mill. Shafts, bars and discs are upset and drawn on hydraulic presses. Forging closes porosity and lines the grain flow up with the shape of the part, which is why a rolled ring is specified over a plate cut-out for cyclic pressure duty.

**Heat treatment.** UNS N10629 is solution annealed, normally between 1050 and 1100 °C, then quenched fast to hold the molybdenum in solid solution. It is not an age hardening alloy. A slow cool or an aging cycle precipitates Ni-Mo intermetallics, which embrittles the part and cuts its corrosion resistance.

**Testing and certification.**

- Chemical analysis by spectrometer, plus PMI on the finished piece where required.
- Mechanical testing: tensile, elongation, reduction of area, hardness and impact.
- Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Liquid penetrant testing to ASTM E165.
- Intergranular corrosion testing to ASTM G28, or a customer specified HCl immersion test to ASTM G31.
- Certificates to EN 10204 3.1 as standard, or 3.2 witnessed by TÜV, SGS, BV, Lloyd's or the customer's own inspector.
- NACE MR0175 / ISO 15156 conformity for sour service when specified at enquiry stage.

## Product forms and size range

| Form | Typical size range | Where it is used |
|---|---|---|
| Seamless rolled rings | OD 200 to 4000 mm, wall 15 to 350 mm, height 20 to 800 mm | Vessel shells, valve seat rings, bearing rings |
| Forged flanges | DN 15 to DN 2000; weld neck, blind, slip-on, orifice | Reactor and column nozzles, piping spools |
| Round bars | 40 to 800 mm diameter, length up to 6000 mm | Valve stems, pump shafts, fastener stock |
| Discs and blanks | 100 to 2500 mm diameter, thickness 20 to 600 mm | Blind covers, closure plates, machining blanks |
| Shafts and spindles | 60 to 800 mm diameter, length up to 8000 mm | Chemical and plunger pumps, agitators |
| Sleeves and bushings | OD 100 to 1500 mm | Compressor and pump wear parts |
| Tube sheets | Up to 3000 mm diameter, drilled or blank | Shell and tube heat exchangers, condensers |
| Valve bodies and parts | To drawing, single piece 5 to 5000 kg | Ball, gate, globe, check and plug valves |

Forgings are supplied black, rough machined with an agreed machining allowance, or finish machined to drawing.

## Applications

- Hydrochloric acid plant: absorbers, strippers, HCl recovery columns, acid storage and transfer pumps.
- Chemical process: reactors, columns and towers, preheaters, crystallizers and process modules handling reducing acids.
- Pressure equipment: heat exchanger tube sheets, shell flanges, nozzle forgings, air receivers.
- Rotating equipment: chemical and plunger pump shafts, agitator spindles, compressor sleeves and bushings.
- Valves: bodies, bonnets, seat rings, stems and blocks for ball, gate, globe, check and plug valves.
- Pharmaceutical, agrochemical, pulp and paper: acetic and formic acid service, digester components.
- Oil and gas: wellhead and Christmas tree components and subsea parts in sour, chloride rich reducing conditions.

## Compared with B-2, B-3 and C-276

| Grade | UNS | Nominal chemistry | Choose it when |
|---|---|---|---|
| Alloy B-2 | N10665 | Ni-28Mo, Cr and Fe kept low | An existing specification calls for it. Allow for HAZ attack and hot working sensitivity. |
| Alloy B-4 | N10629 | Ni-28Mo with 0.5 to 1.5 Cr and 0.1 to 0.5 Al | You want B-2 acid performance with better thermal stability and fabrication behavior. |
| Alloy B-3 | N10675 | Ni-28Mo with about 1.0 to 3.0 Cr | Thermal stability and formability within the Ni-Mo family are the priority. |
| Alloy C-276 | N10276 | Ni-16Cr-16Mo-4W | The process contains oxidizing species, or moves between oxidizing and reducing. |

## Frequently asked questions

**What is UNS N10629?**
UNS N10629 is a wrought nickel-molybdenum alloy with 26 to 30% molybdenum and 65 to 72% nickel, also sold as Alloy B-4 or Hastelloy B-4 and listed in Europe as W.-Nr. 2.4600 / NiMo28Fe4Cr. The composition is held tighter than Alloy B-2 to cut down cracking during fabrication and stress corrosion cracking in service, and it resists hydrochloric acid at all concentrations and temperatures. Jiangyin Jiangnan Metal Co., Ltd. forges it into rings, flanges, shafts, bars and discs.

**Is UNS N10629 the same as Hastelloy B-4?**
Yes. UNS N10629 is the UNS number for the alloy sold as Alloy B-4 or Hastelloy B-4, and as Nimofer 6629 in Europe, where it carries material number 2.4600 with the chemical designation NiMo28Fe4Cr. Hastelloy is a trademark of Haynes International. Material from Jiangyin Jiangnan Metal is made to UNS N10629 chemistry rather than being trademarked product.

**Which standards cover UNS N10629 forgings?**
ASTM B462 covers forged or rolled flanges, forged fittings, valves and parts in UNS N10629 for corrosive high temperature service. ASTM B564 covers nickel alloy forgings generally. Related standards are ASTM B335 for rod, ASTM B333 for plate, sheet and strip, ASTM B622 for seamless pipe and tube, and ASTM B619 and B626 for welded pipe and tube. ASME SB-462 and SB-564 are used for code work.

**Which acids does UNS N10629 resist, and which should it avoid?**
It resists hydrochloric acid at all concentrations and temperatures, plus sulfuric, phosphoric, acetic and formic acid and other reducing media. Keep it out of oxidizing environments such as nitric acid, and out of solutions carrying ferric or cupric ions or dissolved oxygen, which attack nickel-molybdenum alloys quickly. Where the process moves between oxidizing and reducing conditions, choose a Ni-Cr-Mo grade such as C-276 or C-22.

**How does UNS N10629 compare with Alloy B-2 and Alloy B-3?**
All three are Ni-28Mo alloys for hydrochloric acid service. B-2 (N10665) is the original grade and is prone to beta phase precipitation and heat affected zone attack. UNS N10629 (Alloy B-4) holds the composition tighter and adds small chromium and aluminum contents for thermal stability. B-3 (N10675) carries about 1.0 to 3.0% chromium for further thermal stability and formability. All three are supplied solution annealed and are never age hardened.

**Can UNS N10629 forgings be supplied with EN 10204 3.2 certification?**
Yes. EN 10204 3.1 mill certificates are standard, and EN 10204 3.2 certificates witnessed by a third party such as TÜV, SGS, BV or Lloyd's are available on request. Ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388, PMI and corrosion testing can be added to the same package.

**What is the minimum order for UNS N10629 forgings?**
Open-die forging is a one-off process, so single piece orders are accepted as well as production batches. Nickel-molybdenum billet is bought per heat, so small single pieces are usually quoted against material already in stock.

**What information do you need to quote a UNS N10629 forging?**
Send a drawing or the finished dimensions, the quantity, the governing standard such as ASTM B462 or ASTM B564, the delivery condition, any NDT requirement, the certificate type, and the destination port. Email sales@steelforgepieces.com or call +86-189-2135-9659. Quotations are normally returned within 24 hours.

## About the supplier

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, in the Yangtze River forging cluster about two hours from the ports of Shanghai and Ningbo. The plant produces forged and seamless rolled rings, flanges, shafts, bars, discs, sleeves, bushings and tube sheets in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, including the whole nickel-molybdenum family: UNS N10629, Hastelloy B-2, Hastelloy B-3 and Hastelloy B. Enquiries are answered in English and Chinese.

Contact: sales@steelforgepieces.com, +86-189-2135-9659 (WhatsApp and WeChat use the same number).

## Citation

"UNS N10629 forgings, Alloy B-4 (2.4600) data sheet", Jiangyin Jiangnan Metal Co., Ltd., https://www.steelforgepieces.com/Nickel-Alloy/UNS-N10629.html, updated 1 September 2026.

Data compiled from ASTM B462, ASTM B564 and ASTM B335, from published alloy data for UNS N10629, and from the plant's own production records. Values are typical and do not replace the mill certificate supplied with each order.