Hastelloy® G50Trade name
Alloy G-50Generic name · UNS N06950
Summary
Hastelloy G50 and Alloy G-50 are two names for the same material, designated UNS N06950. It is a nickel-chromium-molybdenum-iron alloy used to resist corrosion by sour gas (hydrogen sulfide, H₂S) in oil and gas well service. The alloy contains a minimum of 50% nickel with 19–21% chromium, 15–20% iron and 8–10% molybdenum. Density is 8.33 g/cm³ and the melting point is about 1399 °C. Tensile strength is 760 MPa minimum with a 0.2% yield strength of 700–860 MPa, and hardness is normally held to 31 HRC maximum for sulfide stress cracking resistance.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We manufacture Hastelloy G50, Alloy G-50 and UNS N06950 forged rings, seamless rolled rings, flanges, round bars, discs, sleeves, bushings, tube sheets and shafts to ASTM B564, made to customer drawing. Telephone +86 189 2135 9659. Email sales@steelforgepieces.com.
1. Hastelloy G50, Alloy G-50 and UNS N06950
Ni-Cr-Mo-Fe alloy · one material, three designations
Hastelloy G-50 is the trade-name form of this alloy, Hastelloy® being a registered trademark of Haynes International, Inc. Alloy G-50 is the generic name, used when the grade is bought without reference to a trademark. UNS N06950 is the number assigned to it in the Unified Numbering System. All three describe one nickel-chromium-molybdenum-iron alloy with the same composition limits, the same mechanical requirements and the same heat treatment. A drawing calling for Hastelloy G50 and a purchase order calling for Alloy G-50 are asking for identical material.
Chromium and molybdenum give resistance in both oxidising and reducing environments, and the 15–20% iron content keeps the cost below that of higher-nickel grades. The alloy was developed for sour-gas well service, where hydrogen sulfide causes carbon and low-alloy steels to crack.
| Designation type | Value |
|---|---|
| Trade name | Hastelloy® G-50, Hastelloy® G50 |
| Generic name | Alloy G-50, Alloy G50, G-50 alloy |
| UNS number | N06950 |
| Other trade form | Haynes® G-50 |
| Common misspelling | UNS NO6950 (letter O for zero) |
| Alloy system | Nickel, chromium, molybdenum, iron |
| Forging specification supplied | ASTM B564 |
| Product condition | Solution treated and aged |
Hastelloy G50 and Alloy G-50 belong to the Hastelloy G family, but they are not interchangeable with Hastelloy G-3 or with Hastelloy G-30, which have different compositions and different property requirements. Alloy G-50 is also unrelated to Alloy 50, a nickel-iron magnetic alloy that shares part of the number but nothing else. Please quote the UNS number on enquiries where the drawing is ambiguous.
Hastelloy® and Haynes® are registered trademarks of Haynes International, Inc. They are used on this page only to identify the alloy grade. Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with, endorsed by or licensed by Haynes International, Inc.
2. Chemical composition of Hastelloy G50 / Alloy G-50 (UNS N06950)
Weight percent · nickel is the balance
| Element | Symbol | Content (wt %) |
|---|---|---|
| Nickel | Ni | 50.0 min (balance) |
| Chromium | Cr | 19.0 – 21.0 |
| Iron | Fe | 15.0 – 20.0 |
| Molybdenum | Mo | 8.0 – 10.0 |
| Cobalt | Co | 2.50 max |
| Manganese | Mn | 1.00 max |
| Silicon | Si | 1.00 max |
| Tungsten | W | 1.00 max |
| Niobium | Nb | 0.50 max |
| Copper | Cu | 0.50 max |
| Aluminium | Al | 0.40 max |
| Phosphorus | P | 0.040 max |
| Carbon | C | 0.020 max |
| Sulfur | S | 0.015 max |
Carbon at 0.020% maximum limits grain-boundary carbide precipitation, which protects intergranular corrosion resistance in the heat-affected zone after welding. Sulfur at 0.015% maximum improves hot workability during open-die forging and reduces the sulfide inclusions that act as initiation sites in sour environments.
3. Mechanical properties of Alloy G-50 / Hastelloy G50
Room temperature · solution treated and aged condition
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | ≥ 760 MPa | ≥ 110,000 psi |
| Yield strength (0.2% offset) | 700 – 860 MPa | 102,000 – 125,000 psi |
| Elongation at break (in 50 mm) | ≥ 20 % | ≥ 20 % |
| Modulus of elasticity | 192 GPa | 27,800 ksi |
| Hardness, Rockwell C | ≤ 31 HRC | ≤ 31 HRC |
| Hardness, Brinell (converted) | ≈ 290 HB | ≈ 290 HB |
| Hardness, Vickers (converted) | ≈ 300 HV | ≈ 300 HV |
| Hardness, Knoop (converted) | ≈ 345 HK | ≈ 345 HK |
| Hardness, Rockwell A (converted) | ≈ 66 HRA | ≈ 66 HRA |
Brinell, Vickers, Knoop and Rockwell A figures above are conversions from Rockwell C and are given for reference only. Where a project specification sets a hardness acceptance limit, commonly 31 HRC maximum for sour service, the measured Rockwell C value on the finished forging governs. Please state the test location and frequency on the enquiry.
4. Physical and thermal properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.33 g/cm³ | 0.301 lb/in³ |
| Melting point | 1399 °C | 2550 °F |
| Mean thermal expansion coefficient (20–95 °C) | 13.0 µm/m·°C | 7.22 µin/in·°F |
| Modulus of elasticity (room temperature) | 192 GPa | 27,800 ksi |
At 8.33 g/cm³ a Hastelloy G50 forging weighs roughly 6% more than the same geometry in austenitic stainless steel. This is worth checking before converting a design from stainless to nickel alloy on a weight-priced order.
5. Sour service and corrosion behaviour
Alloy G-50 is intended to resist corrosion by sour gas in oil well applications, and is specified where resistance to sulfide stress cracking is required alongside high strength. Chromium builds a stable passive film in oxidising conditions. Molybdenum carries the resistance into reducing acids and improves pitting and crevice corrosion behaviour in chloride-bearing brines.
Sour-service qualification depends on the service environment. NACE MR0175 / ISO 15156 acceptance is governed by the applicable materials table, the H₂S partial pressure, chloride level, pH and temperature, together with a hardness limit that is commonly 31 HRC maximum. Send the environmental data and the governing specification with your enquiry, and we will confirm in writing the condition and hardness to which the forgings will be supplied.
Selection against neighbouring grades
- Instead of duplex or super duplex stainless steel, when the H₂S partial pressure or temperature exceeds the duplex envelope.
- Instead of Alloy 825 or Incoloy 825, when higher strength is needed at the same corrosion duty.
- Instead of Alloy 718 or Alloy 725, when the strength of a precipitation-hardened grade is not required and cost matters.
Related grades we also forge: Incoloy 825, Incoloy 925, Incoloy 945, Inconel 725, Hastelloy C-276.
6. Melting, heat treatment, welding and machining
Melting route
Hastelloy G50 is melted by EAF + VOD + ESR: electric arc furnace melting, vacuum oxygen decarburisation to reach the 0.020% carbon ceiling, then electroslag remelting to refine the ingot structure, reduce segregation and lower non-metallic inclusion content. The remelting step is what allows large forgings to pass tight ultrasonic acceptance classes.
Heat treatment
Alloy G-50 forgings are supplied solution treated and aged. Reference annealing practice for the alloy is 1149 °C (2100 °F) followed by rapid cooling or water quenching. Final parameters are set against the property and hardness requirements of the order and recorded on the material certificate.
Welding
Hastelloy G50 is welded by gas tungsten arc welding (GTAW/TIG), metal-arc welding and shielded metal-arc welding. Submerged-arc welding is not preferred for this alloy. Control interpass temperature and heat input to protect corrosion resistance in the heat-affected zone.
Machining and cold working
Machining uses conventional methods for iron-based alloys. The material behaves much like an austenitic stainless steel, so rigid setups, positive rake, sharp tooling and generous coolant apply. The alloy can be cold worked with standard tooling and is hardened by cold work. Soft die materials such as zinc alloy and bronze reduce galling.
7. Hastelloy G50 and Alloy G-50 forged product forms
Made to customer drawing or dimension list · rough machined or finish machined
Forged rings and seamless rolled rings
Ring-rolled Hastelloy G50 rings for wellhead, valve and rotating equipment assemblies, with grain flow following the ring circumference.
Forged flanges
Weld-neck, blind, slip-on, orifice and special-bore Alloy G-50 flanges forged to drawing or to the flange standard nominated on the order.
Round bars, hollow bars and shafts
Forged Hastelloy G50 bars, hollow bars, shafts, spindles and eccentric shafts for pumps, compressors and drive trains.
Discs, disks and blocks
Upset-forged Alloy G-50 discs and rectangular blocks for valve bodies, closures, hubs and machined-from-solid components.
Sleeves and bushings
UNS N06950 forged sleeves and bushings for subsea and deepwater production systems, compressors and generators.
Tube sheets
Forged Hastelloy G50 tube sheets for shell-and-tube heat exchangers, drilled or supplied blank for the fabricator to drill.
Forged tubes and pipes
Heavy-wall Alloy G-50 forged tubes, pipes and nozzles for pressure vessels, columns, towers and process modules.
Valve components
UNS N06950 valve stems, seat rings, bodies, plugs and blocks for ball, gate, globe, check and plug valves.
Sizes are made to order. Send a drawing, a sketch with dimensions, or the outside diameter, inside diameter, height and quantity, and we will quote weight, price and delivery.
8. Applications for Hastelloy G50 and Alloy G-50 forgings by industry
Oil and gas
- Wellhead and Christmas tree components, connectors and flexible joints
- Subsea and deepwater offshore production systems, including forged sleeves, bushings and discs
- Sour-gas well hardware where sulfide stress cracking resistance is specified
- Downhole tool bodies, risers, seals and gasket rings
Valves and flow control
- Forged bodies, blocks, valve stems, valve seat rings and plugs
- Ball, gate, globe, check and plug valves, and strainers
Pressure equipment and heat transfer
- Pressure vessels, air receivers, columns, towers, tanks, silos and preheaters
- Shell-and-tube heat exchangers: forged tube sheets, flanges, nozzles and forged tubes
- Process modules and crystalliser equipment
Rotating equipment and power transmission
- Chemical pump and plunger pump shafts
- Industrial air compressors, power generators and nitrogen generators
- Turbine and gas compressor rings, spindles, bars and gear blanks
- Forged crankshafts, rolls and forged wheels for heavy machinery
Chemical, marine and process industry
- Shipbuilding and heavy machinery
- Pulp and paper plant, pharmaceutical and biochemical process equipment
- Cement mills, sugar mills, concrete mills and mixers
9. Testing, certification and traceability
| Check | Standard or method |
|---|---|
| Chemical analysis | Spectrometric analysis, ladle and product analysis reported on the certificate |
| Mechanical testing | Tensile, yield, elongation, reduction of area; impact testing on request |
| Hardness | Rockwell C, reported against the specification limit, commonly 31 HRC max |
| Ultrasonic testing | EN 10228-3, SEP 1921 or ASTM A388, to the class stated on the order |
| Other NDT | Liquid penetrant and, where applicable, magnetic particle examination on request |
| Dimensional inspection | Against the approved drawing, report issued with the shipment |
| Material certificate | EN 10204 3.1 (mill) or EN 10204 3.2 (third-party witnessed) |
| Third-party inspection | TUV, SGS, BV, DNV, Lloyd's Register or the customer's own inspector |
| Marking and traceability | Heat number, alloy grade and order reference hard-stamped or vibro-etched |
Every Hastelloy G50 and Alloy G-50 forging is traceable to its heat and remelted ingot. If your project requires an inspection and test plan (ITP), positive material identification (PMI) at despatch, or a specific witness and hold-point schedule, state it on the enquiry so that it is priced in rather than added later.
10. How to request a Hastelloy G50 or Alloy G-50 quotation
Send a drawing to sales@steelforgepieces.com, or send the six items below and we will quote without a drawing.
- Grade. Hastelloy G50, Alloy G-50 or UNS N06950, and the governing specification such as ASTM B564.
- Shape and dimensions. OD, ID and height for rings; diameter and length for bars; or the drawing.
- Quantity, and whether repeat orders are expected.
- Supply condition. As-forged, rough machined with allowance, or finish machined.
- Testing and certification. UT class, hardness limit, EN 10204 3.1 or 3.2, any third-party witness.
- Service environment. H₂S partial pressure, chloride, pH and temperature, if NACE MR0175 / ISO 15156 applies.
11. Frequently asked questions about Hastelloy G50 and Alloy G-50
Is Hastelloy G50 the same as Alloy G-50?
Yes. Hastelloy G50 and Alloy G-50 are two names for one material, designated UNS N06950. Hastelloy G-50 is the trade-name form, Hastelloy® being a registered trademark of Haynes International, Inc. Alloy G-50 is the generic name used when the grade is bought without reference to a trademark. Haynes G-50, Alloy G50 and UNS NO6950 are further written variants of the same alloy. The composition limits, mechanical requirements and heat treatment are identical whichever name appears on the drawing or purchase order.
What is Hastelloy G50 / Alloy G-50?
Hastelloy G50, also called Alloy G-50 and designated UNS N06950, is a nickel-chromium-molybdenum-iron alloy used to resist corrosion by sour gas (hydrogen sulfide, H₂S) in oil and gas well service. It contains a minimum of 50% nickel with 19–21% chromium, 15–20% iron and 8–10% molybdenum, and combines corrosion resistance with high strength and toughness. Jiangyin Jiangnan Metal Co., Ltd. forges Hastelloy G50 and Alloy G-50 into rings, flanges, bars, discs, sleeves and shafts at its open-die forging plant in Jiangyin, Jiangsu, China.
What is the UNS number for Hastelloy G50?
The UNS designation for Hastelloy G50 is N06950, the same number that applies to Alloy G-50. It is sometimes written incorrectly as UNS NO6950 with the letter O in place of the zero. Orders quoting UNS N06950, Hastelloy G50, Hastelloy G-50, Alloy G-50, Alloy G50 or Haynes G-50 all specify the same alloy.
What is the chemical composition of Alloy G-50 / Hastelloy G50 (UNS N06950)?
In weight percent: nickel 50 min (balance), chromium 19.0–21.0, iron 15.0–20.0, molybdenum 8.0–10.0, cobalt 2.50 max, manganese 1.00 max, silicon 1.00 max, tungsten 1.00 max, niobium 0.50 max, copper 0.50 max, aluminium 0.40 max, phosphorus 0.040 max, carbon 0.020 max and sulfur 0.015 max.
What are the mechanical properties of Hastelloy G50?
At room temperature Hastelloy G50 / Alloy G-50 has a tensile strength of at least 760 MPa (110 ksi), a 0.2% offset yield strength of 700–860 MPa (102–125 ksi), elongation in 50 mm of at least 20%, a modulus of elasticity of 192 GPa, and hardness of 31 HRC maximum, which is approximately 290 HB or 300 HV.
What is the density and melting point of Alloy G-50?
Alloy G-50, also sold as Hastelloy G50 (UNS N06950), has a density of 8.33 g/cm³ (0.301 lb/in³) and a melting point of approximately 1399 °C (2550 °F). Its mean coefficient of thermal expansion between 20 °C and 95 °C is 13.0 µm/m·°C.
Is Hastelloy G50 suitable for sour service?
Yes. Hastelloy G50 / Alloy G-50 was developed to resist corrosion by sour gas in oil well applications, and is specified where resistance to sulfide stress cracking is required. Hardness is normally controlled to 31 HRC maximum. The applicable NACE MR0175 / ISO 15156 table, environmental limits and hardness acceptance criteria must be confirmed against the project specification for each order.
Which standard covers Hastelloy G50 and Alloy G-50 forgings?
Jiangyin Jiangnan Metal supplies Hastelloy G50 and Alloy G-50 forged material to ASTM B564, the standard specification for nickel alloy forgings. Other customer, API or project specifications can be worked to on request.
How is Alloy G-50 melted and heat treated?
We melt Alloy G-50 / Hastelloy G50 by an EAF + VOD + ESR route, that is electric arc furnace melting, vacuum oxygen decarburisation and then electroslag remelting, to control cleanliness and segregation. Forgings are then solution treated and aged. Reference annealing practice for the alloy is 1149 °C (2100 °F) followed by rapid cooling or water quenching.
Can Hastelloy G50 be welded and machined?
Hastelloy G50 / Alloy G-50 is welded by gas tungsten arc welding, metal-arc welding and shielded metal-arc welding. Submerged-arc welding is not preferred. Machining uses conventional methods for iron-based alloys, with characteristics similar to austenitic stainless steels. Cold working is possible with standard tooling, and soft die materials such as zinc alloy and bronze reduce galling.
Which forged shapes are available in Hastelloy G50 and Alloy G-50?
Open-die forged rings, seamless rolled rings, flanges, round bars, hollow bars, discs and disks, sleeves, bushings, tube sheets, shafts, spindles, blocks, valve bodies, valve seat rings, and forged pipes and tubes are all available in Hastelloy G50 / Alloy G-50 (UNS N06950). All shapes are made to the customer's drawing or dimensions.
Who supplies Hastelloy G50 and Alloy G-50 open-die forgings?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No. 1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, that manufactures Hastelloy G50, Alloy G-50 and UNS N06950 forged rings, rolled rings, flanges, bars, discs, sleeves, bushings, tube sheets and shafts to ASTM B564. Enquiries: telephone +86 189 2135 9659, email sales@steelforgepieces.com, website www.steelforgepieces.com.
What certificates and testing are supplied with Hastelloy G50 forgings?
EN 10204 3.1 mill certificates, or EN 10204 3.2 certificates witnessed by a third party such as TUV, SGS, BV, DNV or Lloyd's Register. Ultrasonic testing is carried out to EN 10228-3, SEP 1921 or ASTM A388 as required by the order.
12. About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin City, Jiangsu Province, China. We produce open-die forgings and seamless rolled rings in carbon steel, alloy steel, tool steel, stainless steel and nickel alloys including Hastelloy G50 / Alloy G-50 (UNS N06950). Forged rings, flanges, round bars, discs, sleeves, bushings, tube sheets, shafts and valve components are made to customer drawings for the oil and gas, valve, pressure vessel, power transmission and chemical process industries.
Material is supplied with EN 10204 3.1 or 3.2 certification and ultrasonic testing to EN 10228-3, SEP 1921 or ASTM A388. Enquiries in English or Chinese are welcome.
Page last reviewed and updated: 17 August 2026.
Contact the forging factory
Jiangyin Jiangnan Metal Co., Ltd.
Open-die forging factory
No. 1 Chengxiqiao Road, Zhouzhuang Town
Jiangyin City, Jiangsu Province
China