Tesco Steel & Engineering manufactures Hastelloy C4 flanges (UNS N06455 / W.Nr. 2.4610) — the thermally stable nickel-molybdenum-chromium superalloy with ~65% Ni, ~16% Mo and ~16% Cr, deliberately low in iron, cobalt and tungsten and titanium-stabilized. C4 uniquely resists sigma-phase and carbide precipitation after long exposure at 650–1040°C, keeping ductility and corrosion resistance, plus excellent resistance to hot reducing acids and chloride stress-corrosion cracking. Available in weld neck, slip-on, blind, socket-weld, threaded, lap-joint, spectacle and orifice types to ASTM B564 / ASME B16.5. Class 150 to 2500, NPS 1/2″ to 24″, PN6 to PN400. ISO 9001:2015 certified. Made in India.
Hastelloy C4 (UNS N06455) Flanges
Hastelloy C4 Threaded Flange (Polished)
Tesco Steel & Engineering manufactures C4 flanges in all types from weld neck to orifice, Class 150 to 2500 — supplied with EN 10204 3.1 / 3.2 certification, PMI and third-party inspection on request. Explore the wider Hastelloy flange range, the related Hastelloy C276 flanges and Hastelloy C22 flanges, and the flange dimension charts.
| Hastelloy C4 flanges are available in the following specifications: | |
|---|---|
| Material Grade | Hastelloy C4 / UNS N06455 / W.Nr. 2.4610 (NiMo16Cr16Ti) |
| Alloy Type | Nickel-molybdenum-chromium superalloy (Ni-Mo-Cr), titanium-stabilized |
| Size | 1/2″ NB to 24″ NB (DN 15 to DN 600); larger to ASME B16.47 |
| Class / Rating | 150#, 300#, 600#, 900#, 1500#, 2500# · 3000#, 6000#, 9000# (socket-weld / threaded) |
| Pressure Ratings | PN 6 – PN 400 (PN6, 10, 16, 25, 40, 64, 100, 160, 250, 320, 400) |
| Material Standards | ASTM B564, ASME SB564; EN designation 2.4610 |
| Dimensional Standards | ASME B16.5, ASME B16.47 (Series A & B), MSS SP-44, DIN EN 1092-1 |
| Flange Types | Weld Neck (WNRF), Slip-On (SORF), Blind, Socket Weld (SWRF), Lap Joint, Threaded / Screwed, Spectacle Blind, Long Weld Neck, Orifice, Plate |
| Flange Faces | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G) |
| Weld Filler | ERNiCrMo-7 / ENiCrMo-7 (AWS A5.14 / A5.11) |
| Testing | PMI, hydrostatic, UT, MT/PT per spec; EN 10204 3.1 / 3.2 |
C4 keeps molybdenum and chromium near C276 levels but omits tungsten and minimizes iron and cobalt, with a small titanium addition. This composition is what suppresses sigma-phase and carbide precipitation, giving C4 its hallmark thermal stability. The very low carbon (0.01% max) further protects welds from sensitization.
| Element | Hastelloy C4 (UNS N06455) |
|---|---|
| Nickel (Ni) | Balance (~65%) |
| Molybdenum (Mo) | 14.0 – 17.0% |
| Chromium (Cr) | 14.0 – 18.0% |
| Iron (Fe) | 3.0% max |
| Cobalt (Co) | 2.0% max |
| Titanium (Ti) | 0.70% max (stabilizer) |
| Manganese (Mn) | 1.0% max |
| Carbon (C) | 0.01% max |
| Silicon (Si) | 0.08% max |
| Mechanical Property (solution annealed, typical) | Hastelloy C4 |
|---|---|
| Tensile Strength | 690 – 760 MPa (100–110 ksi) |
| Yield Strength 0.2% | 275 – 345 MPa (40–50 ksi) |
| Elongation | 40 – 60% |
| Hardness | ≤ 100 HRB |
| Density | 8.64 g/cm³ |
| Melting Range | 1350 – 1370 °C |
| Standard | Hastelloy C4 Designation |
|---|---|
| UNS (USA) | N06455 |
| Werkstoff (Germany) | 2.4610 |
| EN designation | NiMo16Cr16Ti |
| ASTM / ASME | B564 / SB564 (forgings); B574, B575, B619, B622 (other forms) |
| Common names | Hastelloy C-4, Alloy C4, Alloy C-4 |
C4 Weld Neck Flange (WNRF)
C4 Slip-On Flange (SORF)
C4 Blind Flange
| Flange Type | Description & C4-Specific Use |
|---|---|
| Weld Neck (WNRF) | Tapered hub butt-welded to pipe for high-integrity, high-temperature corrosive service; weld with ERNiCrMo-7 filler, no PWHT. |
| Slip-On (SORF) | Fillet-welded over the pipe; common in chemical and process piping at moderate pressure. |
| Blind | Seals pipe ends and vessel nozzles in reactors and hot-acid systems. |
| Socket Weld (SWRF) | Small-bore (1/2″–2″) instrument and branch connections in corrosive service. |
| Lap Joint (LJRF) | Used with a C4 stub end where frequent dismantling is required; economizes on alloy in the backing ring. |
| Threaded (TRFF) | Internal NPT/BSP threads for non-welded low-pressure connections. |
| Spectacle Blind / Long Weld Neck / Orifice | Isolation spades, nozzle/long-neck and flow-metering flanges in C4 for elevated-temperature chemical duty. |
| Property | C4 (N06455) | C276 (N10276) | C22 (N06022) |
|---|---|---|---|
| Molybdenum | ~16% | ~16% | ~13% |
| Chromium | ~16% | ~16% | ~22% |
| Tungsten | None | ~3-4% | ~3% |
| Stabilizer | Titanium | — | — |
| Thermal stability | Best (no sigma/carbide) | Good | Good |
| Reducing-acid resistance | Excellent | Excellent | Very good |
| Typical role | Elevated-temp / post-weld stability | Reducing / chloride workhorse | Oxidizing / mixed acids |
Low Fe/Co + Ti stabilization suppress sigma-phase and carbide precipitation at 650–1040°C — stays ductile after long hot exposure.
Excellent in hot contaminated sulphuric, phosphoric and organic acids and chloride solutions.
Very low carbon and titanium stabilization resist HAZ sensitization — usable as-welded without PWHT.
Strong resistance to chloride-induced stress-corrosion cracking and pitting in aggressive media.
| Industry | Typical Application |
|---|---|
| Chemical & Petrochemical | Reactor, column and piping flanges in hot acids and elevated-temperature service |
| Pharmaceutical & Fine Chemicals | Corrosion-critical process and high-purity flanged joints requiring weld stability |
| Flue-Gas & Pollution Control | Scrubber and ducting flanges in acidic chloride service |
| Pickling & Acid Recovery | Hot sulphuric/phosphoric acid line and equipment flanges |
| Heat Exchangers | Tube-sheet and nozzle flanges where post-weld thermal stability is critical |
| Waste & Effluent Treatment | Aggressive mixed-stream flanged connections |
Made from certified C4 with PMI verification of Mo, Cr and Ti — full chemistry confirmed on the MTC.
Manufactured to ASTM B564 / ASME B16.5 in the solution-annealed condition for full corrosion resistance and stability.
WNRF, SORF, blind, socket-weld, threaded, lap-joint, spectacle, LWN, orifice and plate — in RF, FF, RTJ and T&G.
EN 10204 3.1 / 3.2 MTC, heat/lot traceability, hydrostatic and third-party inspection on request.
C4 flange prices reflect the high nickel, molybdenum and chromium content plus forging and machining — it is a premium superalloy for high-temperature and corrosion-critical service. Tesco Steel & Engineering offers competitive ex-works pricing from Mumbai with full export documentation and material traceability. Click Ask for Quote or message us on WhatsApp at +91 92233 66922 with flange type, size (NB), pressure class, quantity and documentation requirements.
Q1. What is a Hastelloy C4 flange?
A Hastelloy C4 flange is a pipe flange made from the nickel-molybdenum-chromium superalloy UNS N06455 (W.Nr. 2.4610) — about 65% nickel with ~16% molybdenum and ~16% chromium, deliberately low in iron, cobalt and tungsten and stabilized with titanium. C4 is the most thermally stable of the Hastelloy C family: it resists sigma-phase and grain-boundary carbide precipitation during long exposure at 650–1040°C, keeping ductility and corrosion resistance. Flanges are forged to ASTM B564 and machined to ASME B16.5 / B16.47 dimensions.
Q2. What is the chemical composition of Hastelloy C4?
Hastelloy C4 (UNS N06455) nominal composition: nickel balance (~65%), molybdenum 14–17%, chromium 14–18%, iron 3% max, cobalt 2% max, titanium 0.7% max (stabilizer), with very low carbon (0.01% max) and silicon (0.08% max). The low iron/cobalt and titanium stabilization are what give C4 its outstanding thermal stability versus C276.
Q3. What is the difference between Hastelloy C4 and C276?
Both are Ni-Mo-Cr alloys with similar Mo and Cr. C276 contains ~3–4% tungsten and more iron, giving slightly broader aqueous corrosion resistance. C4 omits tungsten, keeps iron and cobalt very low and adds titanium, giving superior thermal stability — it resists sigma-phase and carbide precipitation after long exposure in the 650–1040°C range, so it stays ductile and corrosion-resistant where C276 could be embrittled. C4 is preferred where prolonged elevated-temperature exposure or post-weld stability is critical.
Q4. What standards apply to Hastelloy C4 flanges?
Hastelloy C4 flanges are forged to ASTM B564 (UNS N06455) and machined to ASME B16.5 (1/2 inch to 24 inch) or ASME B16.47 / MSS SP-44 for larger sizes, with EN 1092-1 for PN-rated flanges. The European designation is W.Nr. 2.4610 / NiMo16Cr16Ti. Material is supplied with EN 10204 3.1 / 3.2 certification.
Q5. Why is Hastelloy C4 called thermally stable?
Hastelloy C4 is described as thermally stable because its low iron and cobalt content plus titanium stabilization strongly suppress the formation of sigma phase and grain-boundary carbides during prolonged exposure at 650–1040°C. As a result it retains ductility, toughness and corrosion resistance even after long high-temperature service or in the heat-affected zone of welds, where less stable alloys can embrittle and sensitize.
Q6. Can Hastelloy C4 flanges be welded?
Yes. Hastelloy C4 has excellent weldability by GTAW (TIG), GMAW and SMAW using matching ERNiCrMo-7 / ENiCrMo-7 filler. Its low carbon, low silicon and titanium stabilization mean it resists HAZ sensitization, so it can be used in the as-welded condition without post-weld heat treatment in most services.
Q7. What media is Hastelloy C4 resistant to?
Hastelloy C4 resists hot contaminated mineral acids, sulphuric and phosphoric acids, hydrochloric acid at moderate concentrations, organic acids such as acetic and formic, wet chlorine, hypochlorite and chloride solutions, and a range of reducing and mildly oxidizing media. It also resists chloride-induced stress-corrosion cracking. Its key advantage is keeping this resistance after high-temperature exposure.
Q8. What are the mechanical properties of Hastelloy C4?
Typical Hastelloy C4 properties in the solution-annealed condition: tensile strength about 690–760 MPa (100–110 ksi), yield strength about 275–345 MPa (40–50 ksi), elongation about 40–60%, density 8.64 g/cm³. It combines good strength with high ductility and toughness that it retains after thermal exposure.
Q9. What industries use Hastelloy C4 flanges?
Hastelloy C4 flanges are used in chemical and petrochemical processing, especially where equipment sees prolonged elevated temperatures; pharmaceutical and fine-chemical plants; flue-gas and pollution-control systems; pickling and acid-recovery plants; and any service where post-weld thermal stability and resistance to sensitization are critical alongside corrosion resistance.
Q10. Are Hastelloy C4 flanges supplied with material test certificates?
Yes. Every Hastelloy C4 flange is supplied with EN 10204 3.1 (or 3.2) mill test certificates confirming chemistry, mechanical properties and heat/lot traceability, with PMI, hydrostatic testing and third-party inspection on request. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer and exporter from Mumbai, India.