Hastelloy G-3 / Alloy G3 / UNS N06985 Forging Parts

What forged products are available in Hastelloy G-3 / UNS N06985?

Jiangyin Jiangnan Metal produces UNS N06985 through three routes, chosen by geometry and order volume. Open-die forging on 25 MN and 40 MN hydraulic presses covers shafts, blocks, hollow bars and large discs. Seamless ring rolling on radial-axial mills produces G-3 rings from 200 mm to 2,500 mm outside diameter, the usual route for scrubber flanges, pressure-housing rings and rolled-ring blanks. Upset forging handles short, large-cross-section discs and hubs. Because alloy G-3 costs roughly six to eight times the price of 316L per kilogram, near-net-shape forging matters more here than on stainless: profiling the die to the finished contour typically removes 30–50 % of the machining stock and pays for itself on a single order.

• Seamless rolled rings
• Contoured & T-section rings
• Forged discs & tube sheets
• Forged shafts
• Sleeves, bushes & hollow bars
• Valve bodies & bonnets
• Flange blanks
• Forged blocks
• Round / square / flat / hex bars
• Scrubber quencher components
• Pump & agitator shafts
• Custom near-net forgings

What is Hastelloy G-3 (Alloy G3 / UNS N06985)?

Hastelloy G-3 is a solid-solution-strengthened nickel-chromium-iron alloy containing molybdenum and copper, designated UNS N06985 and W.Nr. 2.4619. It sits between the iron-nickel grade Alloy 825 and the high-molybdenum C-family alloys: enough chromium (21.0–23.5 %) for oxidising conditions, enough molybdenum (6.0–8.0 %) for pitting and crevice resistance, and a copper addition (1.5–2.5 %) that specifically improves behaviour in sulfuric and phosphoric acid.

Three composition decisions define the grade in service:

• Carbon capped at 0.015 %. Low carbon suppresses chromium-carbide precipitation at grain boundaries during welding, so the heat-affected zone does not sensitise and the alloy keeps its resistance to intergranular attack in the as-welded condition. This is the single most important difference between G-3 and the older Alloy G it replaced.
• Copper 1.5–2.5 %. Copper lowers the corrosion rate in reducing acids. That is why G-3 is chosen for wet-process phosphoric acid and for sulfuric acid at intermediate concentration, where plain Ni-Cr-Mo alloys perform worse than their molybdenum content suggests.
• Nickel around 44 %. Nickel gives the alloy its resistance to chloride stress-corrosion cracking, the failure mode that eliminates austenitic stainless steels such as 304L and 316L from hot chloride service regardless of their pitting resistance.

Alloy G-3 is not hardenable by heat treatment. It is supplied solution annealed, and any strength above the annealed minimum is obtained by cold work, which is how the cold-worked OCTG grades reach 862 MPa yield. For forgings this means the delivery condition is always solution annealed and rapidly quenched, and any straightening or sizing performed after the anneal has to be controlled so residual cold work does not push hardness outside the sour-service limit.

Typical service: flue-gas desulfurisation quenchers, dampers and outlet ducting; wet-process phosphoric acid evaporators and heat exchangers; sulfuric acid handling equipment; pickling installations; pulp and paper bleach plant; and downhole tubulars, packers and completion hardware in hot sour wells.

What are the equivalent designations of Hastelloy G-3?

Engineers reach this alloy through at least six different names on drawings. They all describe the same chemistry, and Jiangyin Jiangnan Metal Co., Ltd. accepts purchase orders under any of them, supplying UNS N06985 material cross-certified on a single mill test certificate.

Related but not interchangeable: Alloy G-30 (UNS N06030) and Alloy G-35 (UNS N06035) are higher-chromium developments of the same family; Alloy G-50 (UNS N06950) is a higher-molybdenum sour-service variant. Substituting one for another changes the corrosion envelope and must be agreed with the end user.

What is the chemical composition of UNS N06985?

The limits below are the UNS N06985 requirements common to ASTM B581, B582, B622 and the other specifications in the family. Every heat we forge is verified twice: ladle analysis from the melt source, then product analysis on the forged part by optical emission spectrometry. Both results appear on the certificate.

Melting route: G-3 forging stock is normally air-melt + argon-oxygen decarburisation (AOD) or vacuum induction melting (VIM) with electroslag remelting (ESR) where cleanliness matters. For sour-service and nuclear work Jiangyin Jiangnan Metal specifies VIM + ESR stock and reports the melting route on the certificate.

What are the mechanical properties of Hastelloy G-3?

Alloy G-3 cannot be strengthened by heat treatment. The annealed values below are the specified minima that a forging must meet at ambient temperature; the cold-worked line is shown because downhole tubular and packer components are frequently ordered in that condition.

Values are the specified minima for solution-annealed product and typical values for cold-worked product. Actual results for every forging are reported on the EN 10204 certificate, tested per ASTM E8/E8M on coupons taken from the same heat and heat-treatment batch. Test-coupon location (surface, mid-radius or centre) should be stated on the enquiry for sections above 100 mm.

What are the physical properties of Alloy G-3?

Rows marked typical or indicative are representative values for the Ni-Cr-Fe-Mo-Cu family and are given for design guidance only. Where a physical property is contractually significant, for example thermal expansion in a bolted flange stack-up, request the value be verified for the specific heat before ordering.

How is Hastelloy G-3 forged and heat treated?

Alloy G-3 is forged from about 1149 °C (2100 °F) and finished above roughly 927 °C (1700 °F). Below that the alloy work-hardens quickly, forging loads climb and surface cracking risk rises sharply. After the last blow the part must be solution annealed at 1121–1177 °C and cooled rapidly: water quench for heavy sections, forced air for thin ones. Skipping or shortening the post-forge anneal is the most common cause of premature failure in this grade: residual carbides and the deformed structure left by forging both reduce corrosion resistance even though the part will still pass a tensile test.

Diagram: the controlled thermal route applied to every UNS N06985 forging at Jiangyin Jiangnan Metal. Each stage is recorded on the furnace chart and referenced on the EN 10204 certificate.

Numbering here reflects a real production sequence. Each stage must complete before the next begins, and QA sign-off is required at steps 04, 06 and 07.

How corrosion resistant is Hastelloy G-3?

Alloy G-3 was developed to bridge the gap between the iron-nickel grades and the C-family. Its calculated pitting resistance equivalent number is PREN ≈ 45 (Cr + 3.3 Mo at mid-range composition, rising to about 47 if tungsten is counted), roughly double 316L and comparable to the 6 % Mo super-austenitics, but well below C-276. Four behaviours matter in practice:

The comparison against the alloy it superseded is instructive: in laboratory tests G-3 out-performed the earlier Alloy G in 10 % hydrochloric acid, 50 % sulfuric acid, 85 % phosphoric acid, 65 % nitric acid and the mixed ferric/cupric chloride test environment, while the two behaved similarly in 30 % phosphoric acid. Alloy G retained a slight edge only in 10 % sulfuric acid.

Hastelloy G-3 vs C-276, G-30, Alloy 825 and 316L: which should you specify?

The commercial question with G-3 is almost always "can I go down a grade, and where must I go up?" The table compares the alternatives we most often quote against it.

Cost multipliers are indicative ratios of forged material cost per kilogram against 316L, based on our own 2026 purchasing, and move with the LME nickel and ferro-molybdenum indices. Ask for a current spot indication before budgeting.

Is Hastelloy G-3 approved for sour service under NACE MR0175 / ISO 15156?

Yes. UNS N06985 is listed in NACE MR0175 / ISO 15156-3 as a type 4d corrosion-resistant alloy, and it has been used extensively as oil country tubular goods, packers and downhole completion hardware in hot, sour wells. Its combination of nickel and molybdenum extends the sour limits well beyond the stainless grades while retaining resistance to chlorides and dissolved oxygen.

What the listing does not mean is that any G-3 part is automatically acceptable. The qualified envelope in the standard is defined by H₂S partial pressure, chloride concentration, in-situ pH, temperature, elemental sulfur presence and the delivery condition and hardness of the material. Cold-worked G-3 and solution-annealed G-3 are treated differently. Before ordering:

1. State the sour-service requirement on the enquiry, quoting NACE MR0175 / ISO 15156-3 and the edition in force at contract date.
2. Give the environmental data (H₂S partial pressure, chloride, pH, maximum temperature) so the applicable table in the standard can be checked against your duty.
3. Specify the delivery condition (solution annealed, or cold worked to a stated strength level) and the maximum hardness to be verified.
4. Specify where hardness is to be measured. For forgings we map hardness at multiple locations including the mid-wall of heavy sections, and report every reading on the certificate.

How do you weld and machine Alloy G-3?

Welding

Weldability was the point of the G-3 development. With carbon at 0.015 % max and controlled minor elements, the heat-affected zone resists both sensitisation and knife-line attack, so the alloy can generally be used as welded. GTAW and GMAW are the normal processes; matching consumables are AWS A5.14 ERNiCrMo-9 bare wire and AWS A5.11 ENiCrMo-9 covered electrodes. Practical rules: no preheat beyond drying the joint, interpass temperature below 100 °C, stringer beads with minimum weave, heat input controlled to limit hot cracking, and thorough removal of all oxide and grease before welding, because sulfur-bearing contamination causes cracking in every high-nickel alloy. For the most severe acid duties, solution anneal the completed fabrication.

Machining

Alloy G-3 machines like other solid-solution nickel alloys: it work-hardens rapidly and is gummy. Use rigid setups and sharp positive-rake carbide tooling, keep a heavy positive feed so the tool cuts under the work-hardened layer instead of rubbing, run turning speeds in the region of 20–35 m/min with carbide, and flood with coolant. Never dwell. Where a bore above roughly Ø100 mm is required, ordering the part from a trepanned billet rather than a solid forging cuts both material cost and drilling time, a real saving at nickel-alloy prices.

Non-destructive examination

The alloy is austenitic and non-magnetic, so magnetic-particle inspection does not apply. Surface examination is by liquid penetrant per ASTM E165 / E1417; volumetric examination by ultrasonic testing per ASTM A388 or B594 acceptance criteria, noting that coarse-grained nickel-alloy forgings attenuate ultrasound and may need a lower test frequency and a documented calibration block from the same grade.

Production capability: Hastelloy G-3 forging manufacturer

Jiangyin Jiangnan Metal Co., Ltd. has forged open-die parts and seamless rolled rings at Zhouzhuang Town, Jiangyin since 2008, exporting to more than 40 countries. Nickel alloys including UNS N06985 are run on dedicated tooling and in clean furnace atmospheres to avoid sulfur pick-up and cross-contamination from carbon-steel production.

Equipment used for UNS N06985

Machining is performed in-house to rough or finished dimensions. Where a customer-nominated inspector requires witness points, these are scheduled at solution annealing, mechanical testing and final release.

What testing and certification is supplied with G-3 forgings?

Standard supply for every UNS N06985 forging is an EN 10204 3.1 mill test certificate issued by our own quality department, listing heat number, ladle and product chemistry, the solution-annealing cycle actually used, tensile and hardness results, dimensional report and NDE results. EN 10204 3.2 certificates witnessed by DNV, BV, Lloyd's Register, ABS or TÜV are available on request.

How to specify a Hastelloy G-3 forging order

An enquiry that contains the seven items below can be quoted the same day. Anything missing turns into an email round-trip that costs a day each time.

Drawing callout template

Seven mistakes that cost money on G-3 orders

1. Ordering "Hastelloy G-3" on the purchase order. HASTELLOY^® is a Haynes International trademark; strictly read, that order can only be filled by Haynes. Specify UNS N06985 and no one has grounds to reject the material.
2. Omitting the post-forge solution anneal from the specification. The forging will pass its tensile test and fail in acid service. Always state the anneal temperature and the quench.
3. Requesting magnetic-particle inspection. The alloy is non-magnetic, so MT cannot be performed. Specify liquid penetrant instead, or the order stalls at the inspection stage.
4. Assuming G-3 and G-30 are interchangeable. G-30 has 28–31.5 % chromium and behaves differently in oxidising acids. Substitution needs end-user approval in writing.
5. Not stating chloride and H₂S data on a sour-service enquiry. Without the environment, the NACE MR0175 / ISO 15156 table cannot be checked and the compliance statement cannot be issued.
6. Buying a solid billet for a deep-bored part. At nickel-alloy prices, a trepanned or forged-hollow blank commonly saves 40–60 % of the material weight on sleeves and hollow shafts.
7. Leaving the test-coupon location unspecified on heavy sections. Properties at mid-thickness differ from those at the surface. State where the coupon comes from, and the certificate will not be disputed later.

Glossary

Cite this page

This page is maintained as a technical reference by the engineering team at the forge. If you use the data in a specification, report, tender document or answer, please cite it as:

Standards and references

Chemistry, mechanical, heat-treatment and sour-service data on this page are drawn from the published standards and industry references below. Values on any individual certificate are our own test results, traceable to calibrated equipment.

1. ASTM B581, Standard Specification for Nickel-Chromium-Iron-Molybdenum-Copper Alloy Rod, ASTM International, West Conshohocken, PA.
2. ASTM B582, Standard Specification for Nickel-Chromium-Iron-Molybdenum-Copper Alloy Plate, Sheet, and Strip, ASTM International.
3. ASTM B472, Standard Specification for Nickel Alloy Billets and Bars for Reforging, ASTM International.
4. ASTM B564, Standard Specification for Nickel Alloy Forgings, ASTM International.
5. ASTM B622, Standard Specification for Seamless Nickel and Nickel-Cobalt Alloy Pipe and Tube, ASTM International.
6. ASTM B619 / B626, welded pipe and welded tube specifications for nickel alloys, ASTM International.
7. ASTM B366, Standard Specification for Factory-Made Wrought Nickel and Nickel Alloy Fittings, ASTM International.
8. ASTM G28, Standard Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought, Nickel-Rich, Chromium-Bearing Alloys, ASTM International.
9. ASTM E8/E8M, Standard Test Methods for Tension Testing of Metallic Materials; ASTM E112, grain size; ASTM E165 / E1417, liquid penetrant testing; ASTM A388, ultrasonic examination of forgings.
10. NACE MR0175 / ISO 15156-3, Petroleum and natural gas industries — Materials for use in H₂S-containing environments in oil and gas production — Part 3: Cracking-resistant CRAs and other alloys.
11. AWS A5.14 (ERNiCrMo-9) and AWS A5.11 (ENiCrMo-9), filler metal specifications, American Welding Society.
12. EN 10204, Metallic products — Types of inspection documents, CEN, Brussels.
13. Haynes International, HASTELLOY^® alloy G-3 product literature (UNS N06985 / W.Nr. 2.4619).
14. ASM Handbook, Volume 13B, Corrosion: Materials, and Volume 14A, Metalworking: Bulk Forming, ASM International, Materials Park, OH.

Standards are referenced without an edition number because editions change; for procurement, always cite the revision in force at the contract date. All trademarks belong to their respective owners.

Request a quotation for Hastelloy G-3 / UNS N06985 forgings

Other nickel alloys we forge

• Hastelloy C-276
• Hastelloy C-22
• Hastelloy C-4
• Hastelloy C-2000
• Hastelloy B
• Hastelloy B-2
• Hastelloy B-3
• Hastelloy B-4
• Hastelloy X
• Alloy 59
• Alloy 602
• Inconel 600
• Inconel 601
• Inconel 617
• Inconel 625
• Inconel 690
• Inconel 693
• Inconel 725
• Inconel X-750
• Incoloy 800
• Incoloy 800H
• Incoloy 800HT
• Incoloy 825
• Incoloy 890
• Incoloy 901
• Incoloy 925
• Incoloy 926
• Incoloy 945
• Monel 400
• Monel K-500
• Monel R-405
• Waspaloy
• MP35N
• MP159
• Multimet N155
• Haynes 25
• Haynes 188
• Haynes 230
• Rene 41
• NI-SPAN-C 902

Forged in the same grades: forging rings, forged disks, forged cylinders, forging steel products and forging pieces.