2.4879 G-NiCr28W Furnace Fixtures: Composition, Temperature Limits, Design and RFQ Guide

Material number 2.4879, commonly designated G-NiCr28W, is a high-alloy heat-resistant cast material used for selected furnace components. Its nominal nickel-chromium-tungsten concept is intended for hot strength, oxidation-related duty and resistance to demanding furnace atmospheres. It is not Alloy 617, not 310S stainless steel, and not a universal answer for every tray, basket or radiant component.

This guide explains what the designation means, how its major elements interact, why temperature alone is insufficient for selection, and how to specify a 2.4879 furnace fixture. It is written for heat-treatment engineers, maintenance teams and procurement staff. Final material, load, geometry, welding, inspection and maximum operating conditions must follow the furnace owner's approved engineering and the current governing standard.

Identify 2.4879 correctly

2.4879 is associated with the cast designation G-NiCr28W in heat-resistant casting references, including EN 10295 listings. The prefix “G” indicates a cast material. The name reflects a nickel-chromium alloy concept with tungsten; it does not mean that every product form or every manufacturer's proprietary alloy is automatically equivalent.

A Saint-Gobain SEVA product sheet lists EN G-NiCr28W and DIN 2.4879 with a chemistry range centered around high nickel, about 27-30% chromium and 4.0-5.5% tungsten. Those published values are a useful technical reference, but the purchased standard and approved customer specification control acceptance.

Identification item	Correct purchasing approach	Common error
Material number	2.4879 plus G-NiCr28W and the governing standard/edition.	Ordering only “2.4879 alloy” without product form or standard.
Product form	Heat-resistant casting made to an approved drawing.	Assuming wrought plate, forging and casting data are interchangeable.
Temperature	State metal temperature, atmosphere, load, time and cycling.	Using a brochure's maximum air temperature as a design limit.
Equivalence	Engineering comparison of complete specifications.	Calling it Alloy 617, 310S or an ASTM grade based on one element.

Chemical composition and element roles

Published data for G-NiCr28W commonly show carbon around 0.35-0.50%, chromium around 27-30%, nickel around 47-50% and tungsten around 4.0-5.5%, with iron balance and controlled silicon, manganese, phosphorus and sulfur. The exact order limits must come from the cited standard or purchaser specification. A producer's typical analysis is not a substitute for a certified heat analysis.

Element	General role in this alloy concept	Specification boundary
Nickel (Ni)	Supports an austenitic matrix and high-temperature behavior.	High nickel does not alone guarantee creep life or atmosphere resistance.
Chromium (Cr)	Supports protective oxide formation in suitable oxidizing conditions.	Scale behavior depends on atmosphere, cycling and contamination.
Tungsten (W)	Contributes to hot-strength and carbide/solid-solution behavior.	W content must be interpreted with carbon, section and casting process.
Carbon (C)	Influences carbide population, castability and high-temperature strength.	Higher carbon can affect ductility and weld repair response.
Silicon (Si)	Supports deoxidation and can influence oxidation behavior.	Use the specified range; excessive levels can change embrittlement behavior.
P and S	Controlled residuals.	Verify maximums and analytical method in the purchase specification.

Do not confuse 2.4879 with 310S

310S is a wrought austenitic stainless steel concept with substantially lower nickel and no comparable tungsten requirement. G-NiCr28W is a cast, higher-alloy material with different carbon, solidification, carbide structure, design data and fabrication behavior. A tray may contain more than one material only when the design addresses differential expansion, joining and service compatibility.

Selection should compare load, allowable deformation, thermal cycle, atmosphere, repair strategy and cost over the intended campaign. An alloy with a higher nominal temperature in air is not automatically the better choice for a lightly loaded tray, a carburizing atmosphere or frequent water quenching.

Published temperature is not allowable design stress

Supplier references commonly associate G-NiCr28W with maximum air-service values around 1150 C, while some metallographic references discuss use near 1200 C under particular conditions. These values are not a universal continuous-use guarantee. Furnace atmosphere, sulfur potential, carburizing potential, oxygen activity, load stress, section, thermal gradient, dwell and cycling can move the practical limit substantially.

Use time-dependent creep or stress-rupture data at the relevant temperature for loaded designs. A maximum oxidation temperature cannot be used as an allowable stress. The responsible engineer must apply a design method, safety factor, expected section loss and inspection interval appropriate to the fixture.

Temperature question	Data required	Why it matters
Furnace setpoint	Setpoint, overshoot and spatial uniformity.	The fixture may see a different metal temperature.
Metal temperature	Measured or modeled normal and maximum values.	Drives creep, oxidation and expansion.
Time	Dwell per cycle and annual hot hours.	High-temperature deformation is time dependent.
Atmosphere	Air, reducing, carburizing, nitriding, sulfur-bearing, salt or process gas.	Changes scale, internal attack and alloy selection.
Cycling	Heating/cooling rate and quench exposure.	Controls thermal fatigue and shock.

Atmosphere determines more than oxidation rate

In oxidizing service, chromium-rich scale can provide protection when it remains adherent. In reducing, carburizing or sulfur-bearing environments, oxide stability and internal attack differ. Deposits, furnace contaminants and contact with workpieces can create local chemistry not represented by the bulk atmosphere.

Provide gas composition or furnace process rather than the word “heat treatment” alone. Note whether oil residue, salts, boron compounds, copper, zinc, sulfur or carbonaceous deposits can contact the fixture. If molten metal or salt is involved, a dedicated corrosion review is required.

Creep, sagging and load path

Furnace trays usually fail functionally by excessive sagging, cracking, distortion or section loss before simple room-temperature tensile strength becomes relevant. Creep depends on metal temperature, applied stress and time. The load path includes the workpiece, tray ribs, support rails, feet, stacking points and any local contact.

A good RFQ includes maximum gross load, load distribution, center of gravity, stacking arrangement, span, support width and allowable distortion. Point loads and off-center placement should be treated as separate load cases. The new drawing should be reviewed against worn-section conditions, not only full nominal thickness.

Use the actual load map

A total payload number can conceal severe local stress. Show the footprint and mass of each workpiece, temporary fixtures, stacking posts and any robot contact. Include the worst credible asymmetric arrangement and the possibility of a missing or damaged support. The designer can then identify ribs and junctions that require stress, creep or solidification review.

Define allowable deformation

“No deformation” is not a practical engineering criterion for a hot fixture. State the maximum cold sag, twist or interface movement that the furnace, automation and workpiece quality can tolerate. Define the measurement span, temperature condition and datum. A controlled limit permits trend-based retirement before functional interference occurs.

Design input	Minimum RFQ detail	Failure risk if omitted
Gross and net load	Fixture mass, workpiece mass and load per support.	Underestimated creep stress.
Support	Rail spacing, contact width, flatness and movement.	Bending, rocking and local overload.
Stacking	Number of tiers and locating interfaces.	Column instability or contact damage.
Thermal expansion	Clearance, restraint and movement direction.	Buckling, binding or cracked joints.
End-of-life section	Wear/oxidation allowance and retirement criteria.	Unexpected sag or fracture late in campaign.

Thermal expansion and distortion control

High-nickel heat-resistant cast alloys expand appreciably when heated. Ribs, grids and external frames must be arranged so the component can expand without severe restraint. Abrupt stiffness changes and rigid corner locking can concentrate thermal stress. A cold dimensional inspection cannot by itself predict the hot shape.

State cold dimensions and functional hot clearances separately. Identify furnace rails, door openings, robot grippers and workpiece interfaces that can tolerate limited distortion. Datum strategy should reflect how the tray is supported and measured.

Casting design and manufacturing route

2.4879 components may be produced by suitable casting processes chosen for size, geometry, quantity and required surface/detail. Pattern allowance must address alloy shrinkage, machining and anticipated hot distortion. Heavy junctions and isolated bosses need feeding and solidification review.

Do not assume every thin mesh or long rod is best produced as one casting. The design may combine cast sections, approved welds or separately manufactured elements, but every joint changes creep, fatigue and repair behavior. EB Castworld should quote only the manufacturing route supported by the drawing and agreed inspection.

Welding and repair require qualification

High-carbon, high-alloy cast materials require controlled repair planning. Filler composition, joint restraint, preheat/interpass practice, heat input, defect removal and inspection must be qualified for the actual casting and service. A visually acceptable bead is not proof of high-temperature integrity.

Define whether production welds or repair welds are permitted, who approves them, which procedure qualification applies, and what NDT follows. Do not field-weld a loaded furnace tray without the owner's engineering approval. Thermal history and remaining section after service can make a repair unsuitable even when new material was weldable.

Inspection and quality documents

Requirement	What to specify	Evidence
Material	2.4879 / G-NiCr28W, standard edition and chemistry limits.	Heat analysis linked to the casting.
Dimensions	Drawing revision, datums, cold tolerances and CTQs.	Dimensional report and fixture method.
Visual/NDT	Method, coverage, timing and written acceptance.	Inspection report where ordered.
Welds	Permitted zones, WPS/PQR basis and post-repair examination.	Weld map and welder/procedure records.
Traceability	Heat, cast/lot, drawing and part marking.	Certificate-to-part linkage.
Load fit-up	Support, stacking and interface checks.	Trial assembly or gauge result where required.

Receiving and installation checks

At receipt, compare marking, certificate, drawing and packing list before fixtures are mixed. Inspect cracks, transportation damage, straightness, support contact and locating features. Measure critical interfaces on a stable surface using the agreed datums. Quarantine any repaired or distorted component without the required documentation.

During installation, confirm rail spacing, free thermal movement and workpiece distribution. Do not force a tray into a furnace or grind functional sections without approved disposition. Record the initial orientation so future distortion and crack maps can be compared.

In-service inspection and retirement criteria

Create a repeatable map for sag, twist, cracks, oxide loss, rib section and support damage. Measure at comparable cold condition and locations. An arbitrary number of cycles is not a sufficient retirement rule because load and temperature history may differ.

Retirement criteria should address maximum distortion, crack length/location, remaining section, unstable stacking, broken supports and workpiece-quality risk. Trend measurements to schedule replacement before a tray jams automation, damages workpieces or collapses. All hot inspection and handling require the site's isolation, cooling and lifting procedures.

Failure analysis checklist

1. Preserve tray identity, orientation, furnace position and heat/lot.
2. Record temperature history, atmosphere, load, cycles and abnormal events.
3. Map sagging, cracks, oxidation, carburization indicators and support wear.
4. Check whether the load or rail contact changed.
5. Review chemistry, casting, weld and inspection records.
6. Section representative material only under an approved investigation plan.
7. Separate creep, thermal fatigue, corrosion, casting defect and mechanical overload.
8. Validate corrective action on a controlled campaign.

Distortion investigation

Compare the measured shape with support location, temperature zone and load distribution. Uniform long-term sag suggests a different investigation from a sharp local bend at a rail or weld. Review cumulative hot hours and section loss rather than relying only on cycle count. If a tray has been repeatedly inverted, repaired or straightened, record that history because it changes stress and damage.

Crack investigation

Map each crack's origin, direction and relation to a junction, weld, casting surface or contact point. Determine whether it is open at room temperature and whether oxide penetrates the crack. Metallography and chemistry can support the investigation, but the conclusion must also account for restraint, thermal gradient, creep and handling impact.

RFQ checklist for 2.4879 furnace fixtures

1. 2.4879 / G-NiCr28W designation and governing standard edition.
2. Approved 2D/3D drawing, revision, CTQs and casting tolerances.
3. Furnace type, process atmosphere and contaminants.
4. Setpoint, measured metal temperature, dwell, cycles and cooling rate.
5. Workpiece mass/distribution, stacking, rail spacing and allowable sag.
6. Current fixture material, service data, distortion and failure photographs.
7. Casting route, machining and permitted production/repair welds.
8. Chemistry, dimensions, NDT, weld and traceability documents.
9. Quantity, trial plan, packaging, lifting features and destination.
10. Customer retirement criteria and any regulated or safety-critical requirements.

Related products and furnace-fixture guidance

Review G-NiCr28W batch furnace trays, 2.4879 heat-treatment trays and types of heat-treatment fixtures. See quality assurance and factory capability for general manufacturing and inspection context.

Send furnace data and drawings for review

Use the contact page to send the fixture drawing, load map, furnace temperature and atmosphere, current service history, inspection requirements, quantity and destination. Final material, structure and process must be agreed against the customer-approved drawing.

Engineering and safety boundary: Published chemistry, temperature and creep values are reference data, not EB Castworld guarantees. Furnace fixtures are load-bearing hot components; design approval, safe loading, hot handling, inspection interval and retirement decisions remain the responsibility of the furnace owner and qualified engineers.

References

• Saint-Gobain SEVA, G-NiCr28W / DIN 2.4879 product data sheet.
• Schmitz Metallographie, 2.4879 G-NiCr28W microstructure reference.
• Schmidt + Clemens, heat-resistant cast alloys for industrial furnace construction.