Hastelloy C-276 Welding Guide - Filler Metals & Parameters

By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012

Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360

Quick Answer: How Do You Weld Hastelloy C-276?

Hastelloy C-276 (UNS N10276) is welded with a matching nickel-based filler — ERNiCrMo-4 bare wire or ENiCrMo-4 coated electrode — using low heat input, stringer beads, no preheat and no post-weld heat treatment. Interpass temperature stays below about 150 °C (in-house practice), and the joint must be free of iron, zinc, lead and sulphur contamination or the weld will crack.

Key Takeaways

• Match the filler to the base metal, then decide whether to over-alloy. ERNiCrMo-4 is the default for C-276; ERNiCrMo-10 is the default for alloy C-22 (UNS N06022) and is often specified deliberately in oxidizing chloride or mixed-acid duty where the extra chromium pays for itself.
• There is no preheat and no post-weld heat treatment. Nickel-chromium-molybdenum weldments are used as-welded; a post-weld anneal at 600-900 °C is metallurgically harmful, not helpful.
• Heat input and interpass temperature are the two variables you actually control. Keep heat input in roughly the 0.5-1.5 kJ/mm band and interpass below about 150 °C (in-house practice) and most weldability problems disappear.
• Contamination is the number-one cause of cracking. Iron, copper, zinc, lead, tin and sulphur from galvanized fixtures, brass backing bars, marking pencils, lubricants and dirty grinding wheels produce both solidification cracking and heat-affected zone cracking.
• Corrosion qualification is done on the coupon, not on the certificate. ASTM G28 Method A, ASTM G48 and an ASME Section IX qualified procedure are the three documents a process-industry client will ask to see before releasing a C-276 weld.
• Dedicated tooling costs less than a repair. Separate stainless or nickel-alloy brushes, burrs, grinding wheels and lifting gear prevent the iron and carbon pickup that show up later as pitting.

Why Ni-Cr-Mo Alloys Weld Differently from Stainless Steel

Hastelloy C-276 and its relatives do not behave like 316L on the shop floor, and the differences all trace back to chemistry. The alloy is roughly 57% nickel with 14.5-16.5% chromium, 15.0-17.0% molybdenum and 3.0-4.5% tungsten, and the nickel-rich austenitic matrix has a much lower thermal conductivity and a higher coefficient of thermal expansion than carbon steel. Heat therefore stays at the weld pool instead of dissipating, the pool is larger and stays fluid longer, and the surrounding metal moves more during the thermal cycle. The practical consequences are a sluggish, "sticky" weld pool with poorer wetting than stainless, deeper penetration at the same current (a characteristic of nickel-base fillers), and greater distortion on thin sections.

The second difference is that nickel-chromium-molybdenum welding is a slag-free, flux-free process in its common forms. There is no flux to dissolve oxides, so any oxide, oil, paint, moisture or metallic contamination that sits on the joint face goes straight into the pool. Where a stainless welder relies on the flux or on the self-fluxing chromium oxide to absorb dirt, a C-276 welder has to rely on preparation. The alloys also form tenacious, tightly adherent oxides that are difficult to remove mechanically, which is why grinding and cleaning discipline matter more than they do on 316L.

Third, the alloy has almost no tolerance for low-melting-point metallic contamination. Sulphur and phosphorus are deliberately held to 0.030% and 0.040% maximum in ASTM B575 plate, and the filler metal classifications hold similar limits, because higher levels widen the solidification temperature range and produce terminal films at the grain boundaries that tear during cooling. Introduce a few hundred parts per million of lead or tin from a marking pencil or a soldered fitting and the same mechanism produces a crack in a joint that was welded to the book.

Fourth, dilution matters more than in stainless work. The weld metal is not the filler metal — it is a mixture of filler and melted base metal. In a typical single-V groove with manual GTAW, dilution can run 20-40% depending on joint geometry, current and bead technique. That is normally acceptable with a matching C-276 filler, but on a dissimilar joint to carbon steel or low-alloy steel it can pull iron and carbon into the deposit and reduce corrosion resistance. Everything in the rest of this guide — joint design, bead sequence, heat input, travel speed — is ultimately a way of controlling three things: dilution, contamination and thermal cycles.

Base Metals in a C-276 Fabrication: UNS N10276 and Its C-22 Cousin

Hastelloy C-276, UNS N10276, Werkstoff number 2.4819, is the workhorse of the family and the grade most offshore, chemical and flue-gas-desulphurization fabrications are built from. It is supplied as plate, sheet, strip, bar, rod, seamless tube, welded tube and fittings under a family of ASTM specifications that share one chemistry section, so a fabricator can weld a B575 plate to a B622 tube with the same procedure. Its close cousin, Hastelloy C-22 (UNS N06022, 2.4602), carries substantially more chromium — 20.0-22.5% against 14.5-16.5% — and less molybdenum, which makes it the better choice in strongly oxidizing media such as wet chlorine, hypochlorite and ferric or cupric chloride solutions. The two grades are frequently welded to each other in the same vessel.

The most important fabrication fact about both alloys is that they are supplied in the fully annealed (solution-annealed) condition, and that is the condition that should be welded. There is no hardening mechanism to manage and no aging treatment to schedule. A C-276 weldment is finished when it is welded, cleaned and inspected.

Element (wt %)	C-276, UNS N10276	C-22, UNS N06022	Per standard
Nickel	balance	balance	ASTM B575 / ASTM B574
Chromium	14.5-16.5	20.0-22.5	ASTM B575
Molybdenum	15.0-17.0	12.5-14.5	ASTM B575
Tungsten	3.0-4.5	2.5-3.5	ASTM B575
Iron	4.0-7.0	2.0-6.0	ASTM B575
Cobalt	2.5 max	2.5 max	ASTM B575
Carbon	0.010 max	0.015 max	ASTM B575
Silicon	0.08 max	0.08 max	ASTM B575
Manganese	1.00 max	0.50 max	ASTM B575
Vanadium	0.35 max	0.35 max	ASTM B575
Phosphorus	0.040 max	0.020 max	ASTM B575
Sulphur	0.030 max	0.020 max	ASTM B575

Table note: Composition limits as published in ASTM B575 (plate, sheet and strip) and ASTM B574 (bar and rod); the two specifications carry the same chemistry table for these two grades. Filler-metal chemistry is a separate matter and is specified in AWS A5.14 for bare wire and rod and AWS A5.11 for coated electrodes. Verify every heat by PMI before welding; the molybdenum and tungsten levels are what separate a genuine C-276 from a C-4 or C-22 substitution.

A practical PMI point. C-276, C-22 and C-4 are visually indistinguishable, and the discriminator in a positive material identification check is the molybdenum and chromium combination: C-276 runs 15-17% Mo with 14.5-16.5% Cr, C-22 runs 12.5-14.5% Mo with 20-22.5% Cr, and C-4 runs 14-17% Mo with no deliberate tungsten. If a heat is stencilled C-276 but reads 21% chromium, it is C-22 or the plate has been mixed up. Our Hastelloy C-276 plate and bar stock is released against the mill certificate and re-checked by XRF before it leaves the warehouse. For the tube and pipe forms that most process fabrications also need, the same verification logic applies.

Matching Filler Metals and When to Over-Alloy

The default filler for C-276 base metal is ERNiCrMo-4 bare wire or rod for GTAW, GMAW and SAW, and ENiCrMo-4 coated electrode for SMAW. These classification numbers are defined in AWS A5.14 (bare nickel-alloy filler metals) and AWS A5.11 (nickel-alloy coated electrodes for shielded metal arc welding), and both classifications are matched to the UNS N10276 chemistry. For alloy C-22 base metal the matching classifications are ERNiCrMo-10 and ENiCrMo-10. Using the correct classification is not optional: a generic 625-type filler (ERNiCrMo-3) will produce a joint that corrodes preferentially in the weld metal in the media these alloys are bought for.

Over-alloying is the deliberate use of a more highly alloyed filler than the base metal strictly requires. In the C-276 family there are two realistic cases. The first is C-276 base metal welded for oxidizing service — for example a scrubber handling hypochlorite or ferric chloride, where the weld metal needs the higher chromium of an ERNiCrMo-10 or ERNiCrMo-14 deposit to match the corrosion performance of the plate. The second is a joint where dilution from a dissimilar base metal would otherwise degrade the deposit, or where a later repair is likely and the fabricator wants more corrosion margin in place from the start. Over-alloying is not free: the fillers cost more and, in some cases, the higher-molybdenum or higher-chromium deposit is slightly less weldable. It is applied on purpose, with the corrosion test result behind it — never by accident.

Filler classification	Form	Referenced in	Intended base metal	When we recommend it
ERNiCrMo-4	bare wire / rod	AWS A5.14	C-276 (UNS N10276)	Default match for C-276 fabrications, all positions
ENiCrMo-4	coated electrode	AWS A5.11	C-276 (UNS N10276)	SMAW root and fill, repairs, restricted access
ERNiCrMo-10	bare wire / rod	AWS A5.14	C-22 (UNS N06022)	C-22 base metal; over-alloying C-276 for oxidizing media
ENiCrMo-10	coated electrode	AWS A5.11	C-22 (UNS N06022)	SMAW on C-22 and on over-alloyed C-276 joints
ERNiCrMo-14	bare wire / rod	AWS A5.14	C-2000 type	Mixed acid and oxidizing duty where Cr and Mo are both needed
ERNiCrMo-7	bare wire / rod	AWS A5.14	C-4 (UNS N06455)	C-4 base metal; restricted availability outside mill schedules

Table note: Classification designations and the specification numbers they are defined in per AWS A5.14 and AWS A5.11 (latest editions). ERNiCrMo-4 is the standard matching filler for UNS N10276. Our in-house note, not a standard requirement: we do not accept a filler whose certificate shows a molybdenum content below the base-metal range, because dilution then drives the deposit out of the C-276 corrosion envelope.

What weld metal strength should you expect? The base metal is not a high-strength alloy and the weld metal is not either. Undermatching fillers are the rule, not the exception, and this is normal. The mechanical table below gives the base-metal minima from ASTM B575 and typical as-welded all-weld-metal figures from our own procedure qualification records.

Material / condition	Temp	UTS	0.2% yield	Elongation	Per standard
C-276 base metal, solution annealed	20 °C	690 MPa min	283 MPa min	40% min	ASTM B575 / ASTM B574
C-22 base metal, solution annealed	20 °C	690 MPa min	310 MPa min	45% min	ASTM B575 / ASTM B574
ERNiCrMo-4 all-weld-metal, as welded	20 °C	700-760 MPa (typical)	480-560 MPa (typical)	30-40% (typical)	AWS A5.14 classification plus in-house PQR data
C-276 base metal	100 °C	640-680 MPa (typical)	240-270 MPa (typical)	—	Typical values, not a standard minimum
C-276 weld + HAZ, cross-weld tensile	20 °C	Fracture in base metal (typical)	—	—	In-house, not a standard requirement
C-276 weld bend, 4T side bend	20 °C	—	—	No open defect (acceptance)	ASME Section IX acceptance criteria

Table note: Base-metal minima are the specified values in ASTM B575 and ASTM B574. All-weld-metal figures are typical values from our qualification records and are reported for information only; the AWS A5.14 classification sets its own minimum tensile and elongation for all-weld-metal testing, so the controlling document is the classification specification, not this table. Cross-weld tensile tests on matching C-276 joints normally fracture in the base metal, which is the outcome a procedure qualification is looking for.

Welding Processes and Starting Parameters

GTAW is the process of choice for the root pass and for thin material, GMAW with spray transfer is the fastest route for fill on plate, SMAW covers repairs and restricted access, and SAW is reserved for long flat seams where the flux can be kept clean. All four work on C-276, but only if the parameters stay inside a fairly narrow window. The table below is the starting point we give our own customers when they ask what to set the machine to; every number in it is a shop range for a particular joint design, position and welder skill, and none of it is a standard requirement. A qualified welding procedure specification (WPS) supported by a procedure qualification record remains the governing document.

The single most common parameter mistake is running too much current because the pool "feels stiff." Nickel-base fillers have higher electrical resistance than steel fillers, so they heat up along their length and the arc can become unstable at currents that would be comfortable on stainless. The correct response is usually to reduce current, reduce the weave and increase travel speed, not to increase amperage. A wide, hot, slow bead on C-276 produces a large, slowly solidifying pool, a wide heat-affected zone and a high dilution ratio — all three of which push the joint toward cracking and toward corrosion loss in the weld metal.

Process	Filler (typical size)	Polarity	Current range	Shielding / flux	Practical notes
GTAW, manual	ERNiCrMo-4, 2.4 mm rod	DCEN	80-120 A	Argon, 10-14 L/min	2% ceriated or lanthanated tungsten, 3.2 mm; no weave wider than 2-3 rod diameters
GTAW, mechanised	ERNiCrMo-4, 1.2 mm wire	DCEN	110-160 A	Argon, trailing shield recommended	Constant travel speed gives more repeatable dilution than manual work
GMAW, spray transfer	ERNiCrMo-4, 1.2 mm wire	DCEP	150-210 A	Argon or argon-helium, 15-20 L/min	True spray transfer only; short-circuiting transfer gives lack of fusion
SMAW	ENiCrMo-4, 3.2 mm / 4.0 mm	DCEP	80-120 A / 110-150 A	—	Short arc, no whip, dry electrodes; restart areas must be ground
SAW	ERNiCrMo-4, 2.4-3.2 mm wire	DCEP	250-400 A	Matching neutral Ni-Cr-Mo agglomerated flux	Flat position, downhand only; flux must be dry and uncontaminated

Table note: Parameter ranges are typical shop starting values compiled from our in-house welding procedure qualification records and fabricator feedback; they are in-house guidance, not a standard requirement. The controlling documents are the ASME Section IX or ISO 15614 procedure qualification record and the project WPS. Travel speed in the range 75-200 mm/min and heat input in the range 0.5-1.5 kJ/mm are typical for these processes on C-276.

Which process for which joint? For a 6 mm butt on a reactor nozzle, manual GTAW root with ERNiCrMo-4 and GTAW or GMAW fill is the standard answer. For 25 mm plate on a large vessel, GMAW spray transfer with a mechanised carriage cuts hours off the job and produces a more consistent heat input than manual work. For a field repair on a column tray or a pump casing, ENiCrMo-4 coated electrode at 80-120 A with a short arc is the practical answer, provided the area is dry and clean. For SAW, remember that the flux is a chemical product: an agglomerated neutral nickel-alloy flux is required, the flux must be dry, and reclaimed flux must be screened for iron and carbon contamination from the shop floor.

Heat Input, Interpass Temperature and Dilution Control

Heat input is the variable that decides whether a C-276 weld is corrosion-resistant. The rule we work to is simple: use the lowest heat input that still gives full fusion, then stop and let the joint cool before the next pass. High heat input and high interpass temperature do three damaging things at once — they widen the heat-affected zone, they promote the precipitation of molybdenum-rich topologically close-packed phases such as the mu phase in the 600-900 °C range, and they increase dilution by melting more base metal into the pool. The consequence appears later as preferential corrosion attack in the weld metal or in a narrow band on the HAZ side of the fusion line.

The practical controls are: a narrow bevel (60° included angle is usually enough), a small root gap, stringer beads rather than weaves, fast travel, and a forced cool or a moving sequence so that no area of the joint accumulates heat. On thick plate, alternating passes between two welders or two sides, or laying a pass and letting it air cool while the welder works another seam, is ordinary practice. The interpass limit we apply is 150 °C maximum measured 25 mm behind the weld bead with a contact thermometer or an infrared pyrometer, with 100 °C preferred (in-house practice, not a standard requirement).

Parameter	Recommended range	Status	Why it matters
Heat input	0.5-1.5 kJ/mm	In-house practice, not a standard requirement	Controls HAZ width, dilution and precipitation
Interpass temperature	150 °C max, 100 °C preferred	In-house practice, not a standard requirement	Limits phase precipitation and distortion
Preheat	None; base metal at or above ambient (10 °C minimum)	In-house practice	Preheating only worsens heat input and hot cracking risk
Dilution (single-V groove, GTAW root)	20-40% typical	Typical range, dependent on joint design	Sets the actual weld-metal chemistry
Bead technique	Stringer beads, weave ≤ 3x electrode diameter	In-house practice	Reduces pool size, improves solidification pattern
Cooling between passes	Air cool, no forced water quench	In-house practice	A water quench on a hot C-276 joint risks distortion and thermal shock
Post-weld heat treatment	None	Not required, and generally harmful	Thermal exposure at 600-900 °C precipitates detrimental phases
Full anneal if the specification demands it	Approx. 1100-1140 °C plus rapid cooling	Alloy manufacturer guidance, not always achievable on site	Restores the annealed structure after severe cold work or heat exposure

Table note: The heat-input and interpass figures are our in-house fabrication guidance and are not standard requirements; heat input is calculated conventionally as (voltage x current x 60) / (travel speed in mm/min), expressed in kJ/mm. The solution-annealing window reflects published alloy manufacturer guidance and cannot be applied to a fabricated vessel on site — which is precisely why the alloy is designed to be used as-welded.

Dilution control deserves one extra sentence. On a matching C-276-to-C-276 joint the deposit is forgiving, but on a C-276 clad or lined vessel welded to a carbon steel or low-alloy steel shell, or on a dissimilar joint to a stainless flange, dilution dictates the result. On those joints, keep the first C-276 pass low and fast, deposit a buffer layer where the drawing allows it, and never let the arc dwell on the steel side. Where the joint sees a carbon steel root with a C-276 overlay, the overlay should be at least two passes thick so that the surface chemistry is not diluted by the steel below it.

Contamination Control: Iron, Copper, Zinc, Lead, Tin and Sulphur

Contamination, not parameters, is what actually cracks C-276 welds in the field. Nickel-chromium-molybdenum weld metal is highly resistant to general corrosion, and that resistance depends on a very tightly controlled composition: sulphur at 0.030% maximum, phosphorus at 0.040% maximum, and no deliberate additions of lead, tin, zinc or antimony. Every one of those elements lowers the solidus temperature locally, widens the freezing range or forms liquid films at grain boundaries, and the result is a crack that appears either along the centreline of the bead (solidification cracking) or in the heat-affected zone a millimetre or two behind the fusion line (liquation or ductility-dip cracking). None of these defects is visible on a visual inspection, and several are only found by radiography or after a corrosion test.

The sources are almost always mundane. Galvanized fixtures and chain, brass backing bars and copper chill blocks, lead marking pencils, lubricants and cutting fluids containing sulphur or chlorine, dirty grinding wheels previously used on carbon steel or on stainless, wire brushes, slings, and even the welder's gloves. A single pass of a carbon steel wire brush over a C-276 bevel can transfer enough iron and carbon to cause rust staining and local pitting after commissioning.

The controls are equally mundane, and they work: dedicated stainless or nickel-alloy tooling kept separate and stored away from carbon steel, lead-free marking (a scribe or a low-sulphur paint marker), non-chlorinated solvents, dry and clean gas, clean gloves, and a final solvent wipe of every joint face immediately before welding.

Contaminant	Typical sources on site	Failure mode it causes	Control measure
Sulphur and phosphorus	Sulphurized cutting and tapping oils, coolant residues, some marking crayons and tapes, contaminated fluxes	Solidification cracking, HAZ cracking	Sulphur-free consumables, solvent degrease before welding, dedicated cutting tools
Lead	Lead marking pencils, some lubricants and greases, old paint, soldered fittings	Severe hot cracking, even at very low levels	Ban lead marking pencils, use scribes or lead-free markers
Zinc	Galvanized fixtures, ladders, chain, zinc-rich paint, some anti-spatter sprays	Penetration of liquid zinc, cracking, weld porosity	Remove galvanizing, use stainless fixtures, no galvanized supports near the arc
Copper	Brass backing bars, copper chill blocks, copper hammers, copper-plated tools	Hot cracking from low-melting copper phases	Use stainless or ceramic backing, laminate chill bars
Tin	Solders, some platings, contaminated scrap in the fit-up	Grain-boundary liquid films, cracking	Keep solder and plated parts away from the joint
Iron and carbon	Carbon steel brushes, grinding wheels used on steel, steel slings, swarf	Rust staining, local pitting, reduced corrosion resistance	Dedicated stainless or nickel-alloy brushes and wheels, clean and covered storage
Chlorides	Chlorinated solvents, degreasers, marker fluids, tap water cooling	Pitting under deposits, SCC initiation in wet chloride service	Non-chlorinated solvents, demineralized water where rinsing is required

Table note: Failure modes and control measures reflect our in-house fabrication and failure-analysis experience and published metallurgical guidance on nickel-chromium-molybdenum weldability; the chemical limits they relate to are the standard limits in ASTM B575 and in the AWS A5.14/A5.11 filler classifications. These are not themselves standard requirements.

Cleaning, Dedicated Tooling and Stringer-Bead Technique

The correct preparation sequence for a C-276 joint takes minutes and prevents weeks of rework. Degrease the bevel and the surrounding 50 mm with a non-chlorinated solvent and a clean cloth. Remove heat tint, scale and any previously deposited material by machining, carbide burr or grinding with a wheel dedicated to nickel alloys. Wipe again. Fit up with stainless or nickel-alloy fixtures and separation from carbon steel surfaces. Only then strike an arc. Between passes, grind out any visible oxide, arc strike or spatter with the dedicated wheel and blow the area clear with oil-free compressed air or clean argon.

Arc strikes outside the weld area are a specific hazard on these alloys. A stray arc strike creates a local melted-and-resolidified patch with a heat-affected zone beneath it, and in a wet chloride or chloride-bearing process stream that patch becomes a pitting and cracking initiation site. Striking on a run-on or run-off tab, or inside the joint preparation, is the standard remedy. Every arc strike that does occur should be ground out and, if the specification is strict, inspected by dye penetrant.

Stringer-bead technique is the third leg of the same stool. A stringer bead (a bead with essentially no lateral oscillation) has a smaller pool, a steeper solidification front and a lower dilution ratio than a weaved bead at the same current. It also produces a more favourable grain structure, because the successive passes refine one another. Where a weave is unavoidable — say at a corner where access is poor — keep the weave width to no more than about three times the electrode diameter and reduce current to compensate. Never attempt to bridge a wide gap with a single big weave pass; build it up with stringers instead. The same logic applies to the root: a tight, square-edge or small-gap root with a low current root pass outperforms a wide gap filled hot.

Pre-heat, Post-Weld Heat Treatment, Pickling and Repair Welding

There is no preheat for C-276 and there is no post-weld heat treatment. This is not an oversight in the specification — it is the design intent, and it is one of the strongest reasons to choose the alloy. Preheat would only add heat to a material whose weldability depends on staying cool, and a post-weld heat treatment in the 600-900 °C range would precipitate molybdenum-rich phases that reduce ductility and corrosion resistance. If a client's specification asks for post-weld heat treatment on a C-276 weld, the correct response is to query it rather than to comply: the request usually comes from a template written for carbon steel or for stabilized stainless.

What should be done instead is proper weld cleaning and, where the drawing calls for it, mechanical and chemical surface finishing. Heat tint and oxide must be removed mechanically — a stainless wire brush, an abrasive flap disc dedicated to nickel alloys, or a carbide burr — because the tinted layer is chromium-depleted and will corrode preferentially. Nitric acid passivation in the sense used for stainless steel is not the right treatment here: high-molybdenum nickel alloys have limited resistance to nitric acid, and the industry practice is mechanical cleaning followed by a thorough rinse and dry. Where a pickling paste is used at all, it is a nitric-hydrofluoric type applied briefly and completely rinsed, and it is our in-house recommendation, not a standard requirement, to have the fabricator demonstrate the procedure on a scrap coupon first.

Thermal practice is the one part of a C-276 or C-22 fabrication where project documents and shop habit diverge most, so the table below sets out the post-weld thermal sequence step by step, with the basis for each step and the circumstances in which it changes. Read it together with the procedure qualification: ASME Section IX treats preheat and interpass temperature as variables of the welding procedure, which means the limits stated on the WPS are the limits the welder must work to, and going outside them requires requalification. Everything marked typical or in-house in the table is our fabrication guidance and not a standard requirement, and where a purchase specification sets its own thermal cycle, that specification governs.

Thermal step	Recommendation for C-276 / C-22	When it changes	Basis / standard	Note
Preheat	None; base metal at ambient temperature, with about 10 °C as a sensible workshop floor	Only where the purchase specification demands a preheat for the dissimilar carbon steel side of a joint	ASME Section IX treats preheat and interpass temperature as welding procedure variables; the no-preheat rule itself is in-house, not a standard requirement	Preheat adds heat to an alloy whose weldability depends on staying cool and raises hot-cracking risk
Interpass temperature	150 °C maximum, measured on the base metal about 25 mm behind the trailing edge of the bead; 100 °C preferred where the joint will be corrosion tested	Tighten toward 100 °C on thick sections, high-restraint joints and any joint carrying an ASTM G28 acceptance limit	In-house, not a standard requirement; the chosen limit is stated as a variable of the welding procedure per ASME Section IX	A high interpass widens the HAZ, increases dilution and promotes phase precipitation
Post-weld heat treatment (stress relief)	None required; avoid the 600-1000 °C range entirely	Only if a client specification demands a stress relief — query it in writing before complying	ASTM B575 furnishes the alloy in the solution-annealed condition and sets no post-weld heat treatment requirement; ASME Section IX requires any specified cycle to be qualified	Holding weld metal or HAZ at 600-1000 °C precipitates molybdenum-rich phases that reduce ductility and corrosion resistance
Solution annealing (for optimum corrosion resistance)	Not applied to fabricated weldments; where a drawing demands it, approximately 1100-1140 °C (published producer windows extend to about 1150 °C) followed by rapid quench	After severe cold forming, a long high-temperature exposure, or a rejectable corrosion test result	Alloy manufacturer guidance, typical; it is a mill operation rather than a field fabrication step	Requires full-furnace treatment and rapid cooling; distortion and condensation make it impractical on a completed vessel
Residual-stress management instead of PWHT	Manage stress mechanically and procedurally — balanced weld sequence, back-step technique, controlled finishing — rather than thermally	Where cyclic service or a stress-corrosion risk calls for lower residual stress	In-house practice, not a standard requirement; the result is verified by ASTM G28 or ASTM G48 testing	Avoids the deleterious 600-1000 °C precipitation range that a thermal stress relief would enter
Post-weld cleaning: heat tint and oxide removal	Mechanical removal of all heat tint and oxide with a stainless or nickel-alloy wire brush, flap disc or carbide burr, then solvent degrease and rinse	Every weld on a corrosion-resistant item, because the tinted layer is chromium-depleted and corrodes preferentially	ASTM A380 provides the general cleaning, descaling and passivation framework; the tooling rules are in-house practice	Use dedicated tooling — iron or carbon transferred by a steel brush shows up later as rust staining and pitting
Pickling and passivation	Nitric-hydrofluoric pickling paste only where specified, applied briefly, fully rinsed and neutralized; nitric-acid passivation is not applied at all	Where a specification calls for a pickle; demonstrate the procedure on a scrap coupon first	ASTM A967 addresses passivation of stainless steel parts and is not applied to high-molybdenum Ni-Cr-Mo alloys; the recommendation is in-house	High-molybdenum nickel alloys have limited nitric acid resistance, so passivation is not a substitute for mechanical cleaning
Post-weld corrosion verification	Coupon welded with the production filler, thermally treated where the specification requires a simulation, then immersion tested	Wherever an intergranular or pitting acceptance criterion is specified	ASTM G28 Method A (boiling ferric sulfate-sulfuric acid) and the ASTM G48 ferric chloride practices; the acceptance limit is set by the purchase specification	The weakest zone is normally the narrow band immediately behind the fusion line, which is why the coupon is tested rather than assumed

Table note: Post-weld thermal practice for Ni-Cr-Mo weldments in UNS N10276 and UNS N06022, referenced to ASTM B575 (product condition), ASME Section IX (welding procedure variables including preheat and interpass temperature) and ASTM G28 / ASTM G48 (post-weld corrosion verification), with cleaning framed against ASTM A380 and passivation against ASTM A967. Items marked typical or in-house are our fabrication guidance and are not standard requirements; the solution-annealing window reflects alloy manufacturer guidance and is not a field fabrication step.

The same discipline applies in repair welding. A repair should be made with a qualified procedure (or one qualified by the original WPS with only minor changes permitted by the code), the defective area fully excavated to sound metal by grinding, the cavity re-cleaned, the repair welded with the smallest practical number of passes, and the finished repair re-tested by the same method that found the original defect. Repeated repair welding in one location accumulates heat and residual stress, so most project specifications limit the number of repairs and require a metallurgical review beyond the second attempt. Blend the repair flush and re-inspect the surface; a repair that leaves a notch or a rough toe becomes a stress raiser in cyclic service.

Welding Procedure Qualification, Corrosion Testing and Common Defects

A C-276 weld is qualified in two separate ways, and both matter. First, the welding procedure and the welders are qualified under ASME Section IX (or an equivalent such as ISO 15614-1 and ISO 9606-1 outside the ASME world): a procedure qualification record is produced from a test coupon by tensile, bend and, where specified, impact testing, and the welders are performance-qualified on the same joint configuration. Second, and specific to these alloys, the weld zone's corrosion resistance is qualified by an immersion corrosion test on a coupon that has been welded and then, where the specification demands it, thermally treated to simulate service or a stress-relief cycle.

The two standard test methods used for this purpose are ASTM G28, which detects susceptibility to intergranular corrosion in wrought nickel-rich chromium-bearing alloys, and ASTM G48, which measures pitting and crevice corrosion resistance in ferric chloride solution. ASTM G28 Method A is the boiling ferric sulfate-sulfuric acid test, and Method B is the copper-copper sulfate-sulfuric acid test, which is the more aggressive of the two and is applied to the more corrosion-resistant alloys. ASTM G48 Practice A is the ferric chloride pitting test and Practice B is the ferric chloride crevice test; the temperature of the test is selected to suit the alloy, and many project specifications address it by requiring a minimum critical pitting temperature rather than a fixed weight loss.

A realistic acceptance criterion, and one we see most often on offshore and chemical specifications, is a corrosion rate of no more than 5 mpy (about 0.13 mm/year) in ASTM G28 Method A on a welded and sensitization-treated coupon — that is our in-house reading of what a good C-276 weld measures, not a limit written into ASTM G28 itself, which is a test method rather than an acceptance specification. The acceptance limit always belongs to the purchase specification or the client's material specification, and it is worth reading carefully before welding a single coupon.

Test / qualification	Standard	What it detects	Specimen condition	Typical role in a project
Procedure and welder qualification	ASME Section IX (QW-200, QW-300)	Joint integrity: tensile, bend, defect tolerance	As-welded coupon from production materials	Mandatory before production welding
Intergranular corrosion, Method A	ASTM G28 Method A (boiling ferric sulfate-sulfuric acid)	Sensitization and phase precipitation in the weld and HAZ	Welded coupon, plus sensitizing heat treatment where specified	The most widely quoted acceptance test for C-276 weldments
Intergranular corrosion, Method B	ASTM G28 Method B (copper-copper sulfate-sulfuric acid)	Intergranular attack in more resistant alloys	Welded coupon	Used when the project specifies the more aggressive practice
Pitting resistance	ASTM G48 Practice A (ferric chloride)	Critical pitting temperature and pitting attack	Welded and base-metal coupons	Common on offshore and seawater-adjacent projects
Crevice corrosion resistance	ASTM G48 Practice B (ferric chloride crevice)	Attack under gaskets, deposits and crevices	Welded coupon with artificial crevice formers	Specified for flanged and gasketed joints
Positive material identification	ASTM E1476 (guide) with XRF or OES instruments	Grade substitution and filler mix-up	Production material and filler wire	Project pre-weld and post-weld verification

Table note: Standard numbers and their scope as published by ASTM and ASME (latest editions). The 5 mpy figure quoted in the text is our in-house acceptance reading of typical good practice and is not itself a requirement of ASTM G28.

Common defects and what causes them. Almost every C-276 weld defect traces back to one of six causes: too much heat, too much dilution, contamination, poor shielding, poor cleaning, or poor access. The table below is the troubleshooting sheet we keep on the shop floor.

Defect	Appearance	Most likely cause	Corrective action
Solidification (hot) cracking	Centreline crack, often branching	Sulphur, lead or tin contamination; high heat input; deep narrow bead	Remove and re-weld; re-clean joint; ban lead markers; reduce current, use stringers
HAZ liquation or ductility-dip cracking	Crack 1-3 mm behind fusion line	Contamination plus restraint and thermal cycling; high interpass temperature	Control interpass to 150 °C max, reduce restraint where possible, re-qualify the procedure
Porosity	Scattered or clustered gas pores	Damp filler or flux, dirty joint, insufficient or turbulent shielding gas, draughts	Dry consumables, solvent wipe, gas flow and shield checks, wind screens
Lack of fusion / cold lap	Incomplete sidewall fusion on radiograph	Current too low, travel too fast, wrong polarity, sluggish pool not wetted in	Raise current within the qualified range, slow travel, correct technique and angle
Excessive dilution	Weld metal chemistry drifting toward the base metal on a dissimilar joint	High current, wide weave, big root gap	Buffer layer, lower heat input, tighter fit-up, stringer beads
Corrosion attack in the weld zone	Preferential metal loss in weld metal or HAZ during G28 or plant service	Wrong filler, excessive dilution, phase precipitation from high heat input and interpass	Verify filler grade, re-qualify with lower heat input, retest by ASTM G28
Arc burns and spatter	Local melted marks outside the weld	Inadvertent arc strikes, unstable arc	Grind out, dye-penetrant check, use run-on and run-off tabs
Heat tint left in place	Coloured oxide film on the weld and HAZ	No post-weld cleaning	Mechanical removal with dedicated stainless or nickel-alloy tooling

Table note: Defect-cause mapping from our in-house fabrication and failure-analysis records; the acceptance criteria for each defect class come from ASME Section IX or the project's own weld acceptance specification.

A figure worth having on the drawing. Ask your fabricator for a weld-zone corrosion map: a micrograph of the etched cross-section with the fusion line and the HAZ marked, next to the ASTM G28 result for each zone. What that figure normally shows on a well-made C-276 joint is a weld metal and HAZ that both sit inside the corrosion-rate envelope of the parent plate, with a narrow band a fraction of a millimetre wide immediately behind the fusion line that is the first to lose resistance if heat input or interpass temperature was allowed to run high. That narrow band is why the fracture of a C-276 weldment in service so often starts on the HAZ side of the fusion line rather than in the deposit. A figure of this kind, taken from your own coupon, is the single most useful document to attach to a client's corrosion review.

Project Review, Standard Cross-Reference and Commercial Reference

Here is a compact project review of the kind we perform for clients before welding begins. A specialty chemical client asked us to review a weld procedure for a C-276 (UNS N10276) absorber vessel with a 12 mm shell, welded to a stainless steel (316L) inlet flange, in service with chlorinated hydrocarbons plus traces of hydrochloric acid at 90 °C. The procedure as submitted proposed manual GMAW short-circuit transfer with a 625-type filler, an 80° C preheat, a post-weld stress relief at 650 °C and a 4 mm root gap.

Four findings came out of the review. First, the filler classification was wrong for the service: ERNiCrMo-4 was required for the C-276 side, and the dissimilar joint to the stainless flange needed a nickel-base filler on the C-276 side with dilution control, not a short-circuiting transfer mode that produces cold laps on nickel alloys. Second, the preheat was unnecessary and harmful; it was removed. Third, the 650 °C stress relief was a serious metallurgical error and would have precipitated molybdenum-rich phases in the weld metal and HAZ; it was deleted, and the client's specification writer accepted the deletion once the precipitation mechanism was explained. Fourth, the 4 mm root gap was reduced to 2 mm and a machined bevel substituted for flame-cut edges, which cut dilution and removed the oxide problem.

The procedure was re-written with GTAW root and hot-pass at 90-120 A, GMAW spray fill at 170-200 A, interpass limited to 150 °C, stringer beads, dedicated nickel-alloy tooling and a lead-free marking rule on the shop floor. A qualification coupon was welded using the same heat of plate and the same filler batch, then tested by ASME Section IX tensile and bend tests plus an ASTM G28 Method A corrosion test. The G28 result on the welded coupon was roughly 2-3 mpy, comfortably inside the client's 5 mpy limit, and the vessel was fabricated with no weld repairs and no rejectable radiography. That outcome is not unusual — it is what happens when the filler, the heat input and the cleanliness rules are all set before the first arc is struck.

Standard cross-reference. Fabricators working across American, European, Chinese and welding specifications need the numbers mapped in one place. The table below lists the documents that govern a C-276 weldment by function.

Function	US standard	European / ISO route	Chinese equivalent (GB)	Notes
Plate, sheet, strip composition and properties	ASTM B575	EN 10095 / material data sheet for 2.4819	GB/T 15007 (grade NS3304 / H276)	Same chemistry family; property minima differ by system
Bar and rod	ASTM B574	EN 10095	GB/T 15007	Bar limits match the plate chemistry table
Seamless tube and pipe	ASTM B622	EN 10216-5 route or equivalent	GB/T 15062	Check whether tube or pipe is required
Welded pipe and tube	ASTM B619 / ASTM B626	—	—	Filler grade must be stated on the order
Fittings and flanges	ASTM B366	—	—	Chemistry per the applicable product standard
Bare welding filler	AWS A5.14	ISO 18274	GB/T 15620	ERNiCrMo-4 / ERNiCrMo-10 classifications
Coated welding electrodes	AWS A5.11	ISO 14172	GB/T 13814	ENiCrMo-4 / ENiCrMo-10 classifications
Procedure and welder qualification	ASME Section IX	ISO 15614-1 / ISO 9606-1	NB/T 47014	Codes are not interchangeable; re-qualify when switching
Corrosion testing	ASTM G28, ASTM G48	—	GB/T 4334 series (stainless-oriented)	Acceptance limits come from the project specification

Table note: Cross-references are given by scope and subject matter; grade designations across systems are equivalent in intent but are not identical in every limit, so the controlling document must be named on the drawing. GB/T references are listed as the Chinese system counterpart and should be verified against the current edition before use.

Application and parameter selection matrix. Finally, the selection matrix: given what the joint is doing, what filler and what level of control does it need?

Service / joint type	Filler classification	Interpass control	Extra qualification	Reason
C-276 to C-276, reducing acid and chloride service	ERNiCrMo-4 / ENiCrMo-4	150 °C max	ASME Section IX plus ASTM G28 if specified	Matching chemistry gives the best as-welded corrosion envelope
C-276 to C-276, oxidizing chloride or hypochlorite traces	ERNiCrMo-10 (over-alloyed)	150 °C max	ASTM G28 plus ASTM G48	Higher chromium deposit, more margin in oxidizing media
C-22 to C-22	ERNiCrMo-10 / ENiCrMo-10	150 °C max	ASTM G48 preferred	Matching filler for UNS N06022
C-276 to 316L or duplex stainless	ERNiCrMo-4 on the C-276 side, nickel-base buffer where required	150 °C max	ASTM G28 plus cross-weld tensile	Nickel-base deposit tolerates dilution better than a stainless filler would
C-276 to carbon steel or low-alloy steel	ERNiCrMo-4 with a buffer layer	150 °C max, stringers only	ASTM G28, hardness survey on the steel HAZ	Dilution and carbon migration must both be managed
Field repair on a wet chloride line	ENiCrMo-4 coated electrode	150 °C max	Repair procedure approved by the responsible engineer	Fastest, most controllable repair in poor access
Thin sheet, 2 mm and under	ERNiCrMo-4, GTAW only	100 °C preferred	Procedure qualification with bend tests	Arc energy must stay low to avoid burn-through and distortion
Long flat seam on thick plate	ERNiCrMo-4 with matching neutral flux, SAW	150 °C max	Flux and reclaimed-flux cleanliness controls	Highest deposition rate, provided the flux stays clean and dry

Product form	Reference price range (2026)	Comment
C-276 plate	32-48 USD/kg	2026, EXW Shanghai, USD/kg - reference range, floats with nickel price
C-276 bar and rod	30-45 USD/kg	2026, EXW Shanghai, USD/kg - reference range, floats with nickel price
C-276 seamless tube	45-70 USD/kg	2026, EXW Shanghai, USD/kg - reference range, floats with nickel price
ERNiCrMo-4 bare wire 1.2-2.4 mm	45-65 USD/kg	2026, EXW Shanghai, USD/kg - reference range, floats with nickel price
ENiCrMo-4 coated electrode	55-80 USD/kg	2026, EXW Shanghai, USD/kg - reference range, floats with nickel price
Welded C-276 fabrication (shop hours)	Quoted per drawing	Welding and NDT hours normally exceed material cost on small assemblies

Table note: All figures are 2026, EXW Shanghai, USD/kg reference ranges that float with the nickel price and with molybdenum and tungsten raw material levels; they are not quotations and do not include welding, testing or freight. Filler-metal pricing is quoted per kilogram of wire or per electrode, and coated electrode pricing converts to a higher cost per kilogram of deposited metal because of coating weight and stub loss.

Standard Index

Standard	Title / scope	Covers	Form
ASTM B575	Low-carbon Ni-Cr-Mo alloy plate, sheet and strip	Composition, mechanical properties, tolerances	plate, sheet, strip
ASTM B574	Low-carbon Ni-Cr-Mo alloy bar and rod	Composition, mechanical properties	bar, rod
ASTM B622	Ni-Cr-Mo alloy seamless tube and pipe	Composition, mechanical properties, dimensions	seamless tube, pipe
ASTM B619	Ni-Cr-Mo alloy welded pipe	Composition, mechanical properties, dimensions	welded pipe
ASTM B626	Ni-Cr-Mo alloy welded tube	Composition, mechanical properties, dimensions	welded tube
ASTM B366	Nickel-alloy fittings (including Ni-Cr-Mo)	Composition, dimensions, marking	fittings
AWS A5.14	Nickel-alloy bare welding electrodes and rods	Classification chemistry and all-weld-metal properties	bare wire, rod
AWS A5.11	Nickel-alloy coated electrodes for shielded metal arc welding	Classification chemistry and deposited weld metal properties	coated electrode
ISO 18274	Welding consumables, nickel and nickel-alloy bare wire and rod	Classification of filler metals	bare wire, rod
ASME Section IX	Welding, brazing and fusing qualifications	Procedure and welder qualification, acceptance	test coupon
ASME Section VIII Div. 1	Rules for construction of pressure vessels	Design, fabrication, heat treatment rules	vessel
ASTM G28	Detecting susceptibility to intergranular corrosion in wrought nickel-rich chromium-bearing alloys	Method A ferric sulfate-sulfuric acid, Method B copper-copper sulfate-sulfuric acid	test method
ASTM G48	Pitting and crevice corrosion resistance in ferric chloride solution	Practice A pitting, Practice B crevice	test method
ASTM E8/E8M	Tension testing of metallic materials	Test method	test method
ASTM E1476	Standard guide for metals identification, sorting and grade verification	PMI practice	test method
GB/T 15007	Chinese grade designation system for corrosion-resistant alloys	Grade designation and chemistry tables	designation system
GB/T 15620	Chinese specification for nickel-alloy welding wire	Filler classification	bare wire
GB/T 13814	Chinese specification for nickel-alloy covered electrodes	Filler classification	coated electrode

FAQ

Q1: How do you weld Hastelloy C-276?

Hastelloy C-276 (UNS N10276) is welded with a matching nickel-based filler metal — ERNiCrMo-4 bare wire or rod for GTAW, GMAW and SAW, or ENiCrMo-4 coated electrode for SMAW — using low heat input in the region of 0.5-1.5 kJ/mm, stringer beads rather than wide weaves, no preheat, and an interpass temperature held below about 150 °C as our in-house practice. The joint faces are degreased and mechanically cleaned with dedicated nickel-alloy tooling, marking is lead-free, and fixtures are stainless or nickel alloy rather than galvanized or brass. Nothing is added after welding: there is no post-weld heat treatment, only cleaning and inspection. The procedure and the welder must be qualified, normally to ASME Section IX, and where the project specification requires it the weld zone's corrosion resistance is demonstrated by an immersion test such as ASTM G28 Method A. Fabricators who follow those five rules — correct filler, low heat input, cool interpass, clean joint, qualified procedure — weld C-276 routinely without repairs.

Q2: What filler metal should I use for Hastelloy C-276 welding?

The default and correct answer is the ERNiCrMo-4 classification for bare wire and rod, and the ENiCrMo-4 classification for coated electrodes; both are defined in the AWS A5.14 and AWS A5.11 specifications respectively and both are chemistry-matched to UNS N10276. For alloy C-22 (UNS N06022) base metal, the matching classifications are ERNiCrMo-10 and ENiCrMo-10. The filler certificate should be checked before the first arc: a deposit with molybdenum below the C-276 range will not match the base metal's corrosion performance once dilution is taken into account. Deliberate over-alloying is legitimate and common — using ERNiCrMo-10 or ERNiCrMo-14 on a C-276 base metal in oxidizing chloride or mixed-acid service buys corrosion margin in the deposit — but it should be a documented decision backed by a corrosion test, not a substitution of convenience. Never use a 625-type ERNiCrMo-3 filler for a C-276 joint in a chemical process stream; the deposit is not the same alloy and will corrode preferentially.

Q3: Can Hastelloy C-276 be welded to stainless steel or carbon steel?

Yes, but as a dissimilar joint it needs explicit dilution control. C-276 is welded to 316L or duplex stainless routinely on nozzles, flanges and transition pieces, and to carbon steel or low-alloy steel on clad vessels, nozzle reinforcing pads and support attachments. In both cases use a nickel-base filler on the C-276 side — ERNiCrMo-4 is the normal choice — keep the first passes low and fast, and never let the arc dwell on the steel side where dilution pulls iron and carbon into the deposit. For carbon steel joints, a buffer layer of nickel-base filler applied before the C-276 passes is standard practice and is written into most project procedures. The carbon steel heat-affected zone may need a hardness survey where the service is wet sour or where hydrogen is present, and the joint should be qualified as a dissimilar-metal procedure rather than assumed to be covered by the C-276-to-C-276 qualification. On a flanged connection, many fabricators prefer to weld a nickel-alloy stub end to the C-276 and bolt it to the steel flange instead of welding the two metals directly.

Q4: Does Hastelloy C-276 require preheat or post-weld heat treatment?

No. C-276 is welded with the base metal at ambient temperature — a minimum of about 10 °C is a sensible floor for a cold workshop — and no preheat is applied. Preheat only adds energy to a joint whose weldability depends on staying cool, and it increases the risk of solidification cracking. Post-weld heat treatment is likewise not required and is normally harmful: holding C-276 weld metal or heat-affected zone in the 600-900 °C range precipitates molybdenum-rich phases that reduce ductility and corrosion resistance. If a client specification calls for a post-weld stress relief on a C-276 weldment, it has almost certainly been copied from a carbon steel or stabilized stainless template, and it should be queried in writing before welding. The only genuine thermal treatment in the family is a full solution anneal at approximately 1100-1140 °C with rapid cooling, which is a mill operation applied after severe cold forming or a long high-temperature exposure; it is not a fabrication step and is rarely practical on a finished vessel.

Q5: What is the maximum interpass temperature for C-276 welding?

Our in-house limit is 150 °C maximum, measured on the base metal about 25 mm behind the trailing edge of the last bead, with 100 °C preferred on thicker sections and on anywhere the corrosion test is critical. This is fabrication practice rather than a standard requirement, and it sits at the conservative end of what the industry applies: higher limits exist, but they buy nothing and cost corrosion margin. The measurement is worth doing properly — a contact thermometer or an infrared pyrometer, recorded on a pass-by-pass sheet for any joint that will be corrosion tested. Practical ways to stay under the limit include machining a narrower bevel to reduce weld volume, using stringer beads instead of weaves, alternating passes between two sides of a joint or two welders, letting the joint air cool rather than water quenching it, and sequencing work so that a welder moves to another seam rather than waiting. On thin sheet the interpass limit is rarely the problem, but on 20 mm and thicker plate it is often the difference between a 2-3 mpy and a 10 mpy ASTM G28 result.

Q6: Why does my C-276 weld crack?

Cracking in C-276 welds is almost always contamination or heat, and usually both. Solidification cracking running along the centreline of the bead is caused by low-melting-point elements — sulphur, phosphorus, lead, tin, zinc, copper — that are introduced from sulphurized cutting oils, lead marking pencils, galvanized fixtures, brass or copper backing bars, contaminated grinding wheels and dirty brushes. Heat-affected zone cracking a millimetre or two behind the fusion line is driven by the same contamination combined with high heat input, a high interpass temperature and joint restraint. The remedies are procedural, not metallurgical: ban lead and sulphur marking, dedicated stainless or nickel-alloy tooling and grinding wheels, solvent degreasing immediately before welding, stainless fixtures, dry fillers and flux, low heat input, stringer beads, interpass below 150 °C, and a disciplined stop-and-clean between passes. If cracks still appear after all of that, re-examine joint restraint and fit-up, and re-qualify the procedure rather than trying to weld around the problem. Every crack must be excavated to sound metal and re-inspected before a repair pass is laid.

Q7: Can I weld C-276 with Inconel 625 filler?

You can physically weld it, and you will sometimes see it done, but it is not the correct engineering choice for a C-276 process joint. ERNiCrMo-3 (the 625-type classification) has higher niobium and much lower molybdenum than a C-276 deposit, so the weld metal becomes the least corrosion-resistant part of the joint in the very media — reducing acids, chlorides, mixed acid streams — that C-276 was selected for. The failure mode is preferential attack of the weld metal, which usually appears first in an ASTM G28 or ASTM G48 test and later in service as a groove along the weld cap. The legitimate exception is where the joint strength requirement drives the design and the service is not the corrosive one, for example a structural attachment to a C-276 item in a dry environment; even then the choice should be recorded and justified. Substituting Inconel 625 filler to save cost on a C-276 vessel is a false economy, because the repair after the first shutdown costs more than the filler ever would.

Q8: What heat input should be used for Hastelloy C-276 welding?

Our starting band is 0.5-1.5 kJ/mm, calculated conventionally as voltage multiplied by current multiplied by 60, divided by travel speed in millimetres per minute. Within that band we work at the low end for root passes, thin sheet and any joint that will be corrosion tested, and at the upper end only for heavy fill passes on thick plate where fusion is otherwise hard to achieve. Heat input is not a number you set on a machine — it is the result of current, voltage and travel speed together, so a welder who reduces current but slows down has not reduced heat input at all, and a welder who travels faster to compensate for too much current is usually creating lack of fusion rather than a cooler weld. This band is our in-house fabrication guidance, not a standard requirement; where a project specification sets its own heat input range, or sets a maximum interpass temperature, the project number governs. The reason to care is that heat input controls heat-affected zone width, dilution and the precipitation of detrimental phases, all of which show up in the corrosion test result rather than on a visual inspection.

Q9: How is a C-276 weld corrosion-qualified?

In two steps. The procedure and welders are qualified first — normally to ASME Section IX in a US-code project, or to ISO 15614-1 and ISO 9606-1 in a European-code project — using a coupon welded from the production materials with tensile, bend and, where required, impact testing. Then the corrosion behaviour of the weld zone is demonstrated on a coupon, typically by an immersion test: ASTM G28 for intergranular corrosion and ASTM G48 for pitting and crevice corrosion. A good practice is to have the coupon welded by the production welder using the production filler batch, then given any thermal treatment the purchase specification requires to simulate service or a stress relief cycle, and then tested together with a base-metal control sample. The test report should identify the specimen positions (weld metal, fusion line, HAZ and parent plate) separately, because the weakest zone in a C-276 weldment is usually a narrow band immediately behind the fusion line. Acceptance limits are set by the purchase specification, not by the test method.

Q10: What is ASTM G28 and what corrosion rate should I expect?

ASTM G28 is the standard test method for detecting susceptibility to intergranular corrosion in wrought, nickel-rich, chromium-bearing alloys. Method A is the boiling ferric sulfate-sulfuric acid test, and Method B is the copper-copper sulfate-sulfuric acid test, which is the more aggressive of the two and is applied to the more highly alloyed materials. Both work by immersing a weighed specimen in the boiling solution for a defined period and expressing the result as a corrosion rate in mils per year or millimetres per year. For a properly welded C-276 weldment, our in-house acceptance reading of good practice is a rate of no more than about 5 mpy (roughly 0.13 mm/year), and well-made production coupons typically measure 2-3 mpy. Be careful with that number: it is our reading of typical project practice and not a limit written into ASTM G28, which is a test method rather than an acceptance specification. The acceptance limit belongs to your purchase specification, and it should be stated on the drawing before the coupon is welded.

Q11: What shielding gas and tungsten electrode should be used for GTAW on C-276?

Argon at roughly 10-14 litres per minute is the standard shielding gas for manual GTAW on C-276, with a 2% ceriated or lanthanated tungsten electrode of about 3.2 mm diameter for work in the 80-120 A range and DCEN polarity. Argon-helium mixtures are sometimes used to increase penetration and heat input on thicker sections, and for mechanised or orbital work a trailing shield is worth fitting to protect the cooling weld from oxidation. Two details matter more than the gas choice. First, gas delivery has to be clean and dry: moisture and oil from a contaminated line, or turbulence from too high a flow rate that draws in shop air, are the classic causes of porosity. Second, the tungsten must not touch the pool — tungsten inclusions are a rejectable defect and they also disturb the arc and the bead profile. Purge the gas line before starting, set flow with a flowmeter rather than by ear, and use wind screens if any door, fan or open bay is creating draught across the joint.

Q12: Can a C-276 weld be repaired, and how many times?

Yes, repair welding is normal, and it is governed by the same rules as the original weld plus a few extra ones. The defective area is excavated completely to sound metal by grinding with dedicated tooling, the cavity is re-cleaned and degreased, and the repair is welded with a qualified procedure using the matching filler and the smallest practical number of passes, at the same low heat input and interpass limits. The repair is then re-tested by the method that found the original defect — radiography, dye penetrant or ultrasonic — and a corrosion test coupon may be required if the repair is in a critical process area. Because each repair adds heat, restraint and residual stress, most project specifications limit the number of repairs in one location, commonly to two, with a metallurgical review and client approval beyond that. Welding over a crack without excavation is never acceptable: the crack will re-open, propagate into the heat-affected zone and, in wet chloride service, become a stress-corrosion cracking initiation site.

Q13: How should a C-276 weld be cleaned after welding?

Mechanically, and with dedicated tooling. Heat tint and oxide left on a C-276 weld are chromium-depleted and will corrode preferentially, so the weld cap, the toes and both sides of the heat-affected zone are cleaned back to bright metal — a stainless steel wire brush used only on nickel alloys, a flap disc or an abrasive wheel kept for nickel alloys, or a carbide burr for restricted areas. Solvent degreasing follows, with a non-chlorinated solvent, and the surface is rinsed and dried. Nitric acid passivation in the sense used for stainless steel is not appropriate for high-molybdenum nickel alloys, which have limited resistance to nitric acid, and our in-house guidance is to avoid passivation as a substitute for mechanical cleaning. Where a pickling paste is specified, it is normally a nitric-hydrofluoric type applied briefly, fully rinsed and then neutralized, and we recommend that the fabricator prove the procedure on a scrap coupon and check the result with a corrosion test before it is applied to a pressure part. Iron contamination introduced by a carbon steel brush shows up as rust staining within days of commissioning.

Q14: How does C-276 compare with C-22 for welding?

Both weld with the same rules — nickel-base matching filler, low heat input, stringer beads, no preheat, no post-weld heat treatment, interpass below about 150 °C, and strict contamination control — so a fabricator who can weld one can weld the other. The differences are in the filler selection and in the service the joint suits. C-276 uses ERNiCrMo-4; C-22 uses ERNiCrMo-10, which carries more chromium and less molybdenum. C-22 has an advantage in strongly oxidizing media such as wet chlorine, hypochlorite and ferric or cupric chloride solutions, while C-276 remains a strong performer in reducing acids and in chloride-bearing environments generally. Because the two grades are frequently welded to each other in the same vessel, it is good practice to keep both filler classifications in the stores with clear labelling, and to state the filler on the weld map rather than on the shop floor's memory. Our historical comparison guides walk through the service-selection differences in more detail, and the knowledge center holds the corrosion data behind those recommendations.

Conclusion: Weld It Cold, Clean and Qualified

Hastelloy C-276 is one of the most weldable of the high-performance nickel alloys, precisely because its designers removed the two hardest things about welding a high-strength alloy: it needs no preheat and no post-weld heat treatment. What it demands instead is discipline in four areas — the right filler classification (ERNiCrMo-4 or ENiCrMo-4 for C-276, ERNiCrMo-10 for C-22, over-alloyed where oxidizing service justifies it), heat input and interpass control within the bands given above, absolute cleanliness with dedicated tooling and lead-free marking, and a qualified procedure backed by a corrosion test on a real coupon. Get those four right and the corrosion resistance of the joint matches the plate it connects. Get any one of them wrong and the weakest point in the assembly becomes a narrow band behind the fusion line that will not show up until the shutdown.

If you are preparing a purchase specification, a WPS review or a bid for a C-276 fabrication, send us the drawing, the filler certificate and the proposed procedure and we will review them against the standard requirements and against our own qualification records. We also stock the matching filler classifications and the Inconel alloy and Monel families that appear alongside C-276 in process plants. For a review, a quotation or a data pack, use our quotation and enquiry desk and we will respond with technical comments rather than a bare price.

Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier — ISO 9001:2015, established 2012 — supplies Hastelloy C-276 plate, bar, tube and fittings with EN 10204 3.1 certification, PMI verification and third-party inspection on request.

Email: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360

Contact & Complete Product Range

Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier

Email: sales@hangboalloy.com | WhatsApp (Lisa): +86 13611656360 | www.nickel-alloy.com

All Grades

Ni: NI200-N6 | Monel: 400-502, K-500, R-405 | Inconel: 600-740H, X-750, 725 | Incoloy: 800-27-7MO | Hastelloy: C-276-HYBRID-BC1, N | Super Austenitic: 904L-AL-6XN | Chromium-Rich: Alloy 33 | High-Strength Stainless: Nitronic 50/60, PH13-8Mo | Chlorination: Alloy 45 | Nimonic: 75-263 | Haynes: 25-HR-160 | RA: 330/333 | Precision: 1J22-4J45 | High-Strength: 18Ni250-AerMet100 | Heating: Cr20Ni80/60 | Specialty: Alloy 20-602CA

Product Forms: Bars(6-500mm) | Tubes(OD 6-610mm) | Plates(0.1-100mm) | Forgings | Welded Pipes | Fittings | Wire(0.05-10mm) | Strip(0.02-4.0mm)

SGS/BV/TUV. www.nickel-alloy.com