OFE Copper Investment Casting: OFHC and ETP High-Purity Copper Grades - Alloy Selection, Properties and Procurement Guide

The Bottom Line

• High-purity copper investment casting spans three distinct grades - ETP, OFHC, and OFE - and getting the right one cast correctly is what determines whether a switchgear, transformer, or induction-heating component actually holds its rated conductivity in service.

• ETP copper (C11000) is the cost-effective default for the majority of current-carrying castings; OFHC (C10200) and OFE (C10100, cast as C80100) are vacuum-melted grades required wherever hydrogen exposure or an absolute purity ceiling is non-negotiable.

  
  

• Conductivity is won or lost at the melt, not the machine shop - vacuum melting for OFHC/OFE and controlled-atmosphere melting for ETP are what preserve IACS through to the finished casting, not a downstream fix.

  
  

• Pure and near-pure copper is genuinely difficult to cast - prone to shrinkage, cracking, and gas porosity - which is exactly the process discipline OFE copper investment casting has to solve for, and why it exists as its own specialized capability, not a generic casting service.

Why High-Purity Copper Needs Its Own Category - Not Just "Purer Is Better"

OFE copper investment casting, OFHC copper investment casting, and ETP copper investment casting are often treated as one spectrum - pick the highest grade affordable and assume it's the safest choice. That instinct gets the decision backwards. All three grades deliver conductivity in the same 100 to 101-plus percent IACS range; what actually separates them is oxygen content, melting process, and what that means once a part meets a specific service condition - a hydrogen-bearing atmosphere, a brazing operation, or an absolute purity ceiling a specification demands. A busbar connector that never sees a reducing atmosphere doesn't need OFE's purity margin. A vacuum interrupter component that will be brazed into an assembly can't safely use anything less than an oxygen-free grade.

The full selection framework - including when near-net-shape casting itself is the bigger value driver than the grade decision alone - is covered in choosing between OFE, OFHC, and ETP grades. This pillar guide covers the three grades as a complete high purity copper casting resource: the properties that separate them, the dedicated cast specification that exists for pure copper specifically, where each grade is actually specified across transformer, switchgear, and induction-heating hardware, and what to put on a drawing to get the grade actually delivered.

Cost tracks the same order as purity, and that matters for how the decision should actually be made. ETP is the least expensive of the three because it's air melted under ordinary atmosphere control; OFHC costs more because vacuum melting is a slower, more equipment-intensive process; OFE costs more again because its 5 ppm oxygen ceiling demands tighter process control than OFHC's 10 ppm. None of that premium is wasted when the application genuinely needs it - a vacuum interrupter contact that fails from hydrogen embrittlement costs far more in downtime and warranty exposure than the grade premium would have. The premium is wasted when it's paid by default, on a part that never approaches the service condition the higher grade exists to solve for. That's the core discipline this pillar and its cluster articles are built around: match the grade to the condition, not to the highest number on the spec sheet.

OFE Copper Investment Casting vs OFHC and ETP: The Grades Compared

The three grades share one thing - all are considered high purity copper casting options - and differ everywhere else that matters to a specifier:

Grade	UNS	EN	Melting Process	Oxygen Content	Typical IACS
ETP Copper	C11000	Cu-ETP, CW004A	Air melted, controlled atmosphere	~0.02-0.05% (200-500 ppm)	100-101% (properly melted)
OFHC Copper	C10200	Cu-OF, CW008A	Vacuum melted	10 ppm maximum	100%+ minimum
OFE Copper	C10100	Cu-OFE, CW009A	Vacuum melted	5 ppm maximum	101%+ minimum
C80100 (dedicated cast spec)	C80100	Cu-C, CC040A	Vacuum/controlled melting, cast form	Tightly controlled	93% IACS minimum, up to 100%

IACS - International Annealed Copper Standard - is the reference scale conductivity is measured against, with pure annealed copper defined as the 100 percent baseline. A casting reading 101 percent IACS is conducting marginally better than that reference standard; one reading 85 percent is losing a meaningful fraction of its current-carrying or heat-dissipating capacity to scattering effects from oxides, gas porosity, or retained impurities. For a buyer, the number on a material certificate is only meaningful if it was actually measured on the production heat, not assumed from the alloy's nominal specification - a point the specification section further down covers in detail.

Conductivity in a finished casting is a melt-quality outcome, not a material-selection outcome alone. ETP's oxygen content has to be controlled through atmosphere and fluxing discipline during air melting to land in its 100 to 101 percent IACS range - the same melt control covered in why a copper casting failed conductivity test. OFHC and OFE copper investment casting requires vacuum melting specifically because their oxygen ceilings - 10 ppm and 5 ppm respectively - are below what atmosphere control alone can reliably hold; the vacuum removes the oxygen source rather than managing it, a process discipline covered in more depth in OFHC copper investment casting vs hot forging, including why hot forging's heat and deformation degrade the same conductivity vacuum melting protects.

That difference in melt atmosphere is also what makes OFHC and OFE copper immune to hydrogen embrittlement, a real service-life risk in ETP copper once it's exposed to a hydrogen-bearing atmosphere above roughly 370 to 400 degrees C. ETP's cuprous oxide reacts with hydrogen to form steam at grain boundaries above that threshold; OFHC and OFE simply don't carry enough oxide for the reaction to occur in any meaningful degree. The full mechanism, temperature thresholds, and prevention practice are covered in hydrogen embrittlement in ETP copper casting - required reading for any buyer whose ETP application involves brazing, welding, or a hydrogen-bearing process downstream of casting.

C80100: The Direct Investment-Cast Equivalent of Wrought OFE Copper

OFE, OFHC, and ETP as UNS numbers - C10100, C10200, C11000 - are technically wrought copper designations, defined for rod, bar, and sheet. Investment casting - also known as lost wax casting - is what lets Pahwa MetalTech deliver that same chemistry and conductivity as a near-net-shape part instead of material a buyer would otherwise have to machine from stock.

Pure copper is a genuinely difficult metal to cast on its own: it's prone to shrinkage porosity, hot cracking, and gas pickup during solidification in ways the wrought specifications were never written to address, because they assume the metal is already solid, worked material by the time a spec applies to it.

C80100 (EN Cu-C, CC040A under EN 1982, JIS CAC101) is copper's own answer to that gap - a specification written for the cast condition specifically, not adapted from a wrought one. It carries a minimum 99.95 percent copper content and a guaranteed minimum conductivity of 93 percent IACS under EN 1982, with well-controlled castings reaching up to 100 percent - stated as an honest range here rather than a flat headline number, the same way Pahwa's own ETP casting specification is stated as a guaranteed minimum rather than a best-case figure.

For a buyer specifying a cast pure-copper part, naming C80100 directly - alongside the OFE/OFHC conductivity and oxygen requirements that actually matter for the application - removes any ambiguity about whether a wrought spec is being awkwardly retrofit onto a casting.

In practice, C80100 shows up on drawings for electrical switchgear hardware and electrode holders - parts where the buyer needs cast pure copper's near-100-percent conductivity and near-net-shape geometry together, and where naming the dedicated cast specification is more precise than naming a wrought grade and hoping the foundry interprets it correctly for a cast part. The full C80100 specification breakdown - composition limits, verification protocol, and how it maps against the OFE conductivity a spec writer may already be targeting - is covered in C80100 investment casting.

C80100 sits within Pahwa MetalTech's wider copper alloy investment casting capability, which spans high-conductivity coppers alongside aluminium bronzes, tin bronzes, and other copper alloy families — see the full copper alloys casting range for the complete list.

Where High-Purity Copper Castings Are Used: Transformers, GIS, Induction Heating, and Green Hydrogen

High purity copper casting shows up wherever a component has to carry serious current or heat flux and can't afford a conductivity penalty for the sake of convenience. Four buyer groups make up the large majority of demand:

• Transformer OEMs - bushing conductors, tap-changer contacts, neutral grounding connections, and terminal hardware, where contact resistance directly drives localized heating and, over enough service life, insulation degradation around the joint.

  
  

• GIS (gas-insulated switchgear) manufacturers - contact assemblies, disconnector links, current transformer windings, and busbar hardware operating inside a sealed, pressurized environment where a field failure means an outage and a specialized repair, not a simple swap.

  
  

• Induction heating engineers - work coils, susceptor mounting hardware, and induction furnace current-carrying components, where both electrical conductivity and thermal conductivity are active design constraints simultaneously, not just one or the other.

  
  

• Green hydrogen developers - electrolyzer bipolar plate current collectors, PEM stack busbars, and stack terminal hardware, where the operating environment itself can be hydrogen-bearing - making the choice between ETP and an oxygen-free grade a first-order design decision, not a detail.

Across all four, the pattern from the grade-selection section above repeats: ETP covers the hardware that stays clear of hydrogen exposure at elevated temperature, and OFHC or OFE becomes mandatory the moment brazing, welding, or a hydrogen-bearing process enters the picture - electrolyzer hardware and any bushing or terminal assembly joined by brazing being the clearest examples.

Transformer and GIS hardware make up the largest share of demand in this category, and the two buyer groups share a common failure mode to design against: a connector or contact that meets its conductivity spec on day one but degrades in service because contact resistance was never actually verified under load, only inferred from composition.

Pahwa MetalTech's own electrical and switchgear casting work covers this same hardware directly — bus bar fittings and connectors, arc chute and interruption chamber parts, instrument transformer housings, isolator components, and contact bodies.

A bushing terminal running hotter than its neighbors under identical load is very often a conductivity problem hiding behind a passed incoming inspection - which is exactly why the specification and verification practices covered later in this guide matter as much as the grade decision itself. GIS hardware adds one further constraint on top: a contact assembly or busbar joint sealed inside a pressurized gas-insulated enclosure is expensive and slow to access if it fails, which is why GIS buyers tend to specify tighter conductivity margins than the minimum an application would technically need - the cost of over-specifying a few percent of IACS is trivial next to the cost of an internal fault in a sealed switchgear bay.

Induction heating is a different kind of demanding: coil and inductor components carry both high-frequency electrical current and significant thermal load simultaneously, so both electrical and thermal conductivity are live design constraints at once, not a single property to optimize. Copper's thermal conductivity tracks its electrical conductivity closely across the OFE, OFHC, and ETP range, which means the same melt-quality discipline that protects IACS also protects heat dissipation - a coil casting with gas porosity or oxide inclusions runs both electrically resistive and thermally insulating exactly where a designer needs neither.

Green hydrogen is the newest and fastest-growing of the four segments, and it inverts the usual default. Where switchgear and transformer hardware can often default to ETP unless a specific condition rules it out, electrolyzer current-carrying hardware operates inside a hydrogen-bearing environment by definition - making an oxygen-free grade the starting assumption, not a special case to justify. Buyers new to specifying copper for this application sometimes carry over ETP defaults from adjacent electrical work; the hydrogen embrittlement in ETP copper casting mechanism explains exactly why that default doesn't survive contact with an electrolyzer's actual operating environment.

For switchgear specifically, pure copper vs CuCrZr for switchgear contact blocks goes a level deeper - covering when a pure copper grade's conductivity wins the decision outright, and when CuCrZr's added strength changes the answer instead.

All four segments are growing for reasons that trace back to the same grid: transformer and GIS demand tracks grid modernization and renewable interconnection, both of which add more switching and transformation points to the network rather than fewer; induction heating demand tracks industrial electrification generally; and green hydrogen demand tracks electrolyzer capacity additions directly, which is why it's been the fastest-moving of the four segments even though it's the newest. None of that growth changes the underlying selection logic - it just means more buyers are encountering the OFE-vs-OFHC-vs-ETP decision for the first time, often without a background in why the three grades differ.

Not every high-conductivity copper casting application is electrical in the switchgear or transformer sense. Thermal management is a distinct and fast-growing use case for the same high-purity, vacuum-melted copper grades - EV power module cold plates and AI data-center cold plates both depend on the identical low-porosity, high-IACS casting discipline covered throughout this guide, just applied to heat dissipation rather than current-carrying capacity. That side of high-conductivity copper investment casting is covered in investment casting for copper heat sinks.

Common Failure Modes in High-Purity Copper Castings

Most quality escapes in high purity copper casting trace back to one of three root causes, and each is preventable with the right melt and specification discipline rather than after-the-fact inspection alone:

• Conductivity shortfall despite a correct composition certificate - a casting can pass chemistry and still fail an IACS test, because gas porosity and oxide inclusions from an uncontrolled melt scatter conduction electrons in ways a composition certificate never catches. Covered in full in why a copper casting failed conductivity test.

  
  

• Hydrogen embrittlement in ETP copper exposed to a hydrogen-bearing atmosphere after casting - the Cu2O naturally present in ETP reacts with hydrogen to form steam at grain boundaries, causing internal cracking that can pass every dimensional inspection before failing in service. Covered in hydrogen embrittlement in ETP copper casting.

  
  

• Gas porosity from uncontrolled atmosphere melting - hydrogen and oxygen absorbed during melting are expelled on solidification, forming voids that degrade both mechanical integrity and electrical conductivity, addressed in gas porosity in pure copper casting.

All three trace back to the same root cause from different angles: melt atmosphere and process discipline, not the alloy specification itself. A correct UNS number on a drawing guarantees nothing about how the metal was actually melted - which is exactly why the specification section below treats a measured conductivity result, not just a composition certificate, as the real proof of a properly made casting.

What to Specify When Ordering High-Purity Copper Investment Castings

A drawing that names a family - "oxygen-free copper," "high conductivity copper" - without a UNS or EN code and a measurable conductivity requirement leaves the actual grade delivered open to interpretation. A complete specification for OFHC copper casting or any high-purity grade states four things and asks for the paperwork that proves them:

Specification Item	What to State	Why It Matters
Alloy designation	UNS and EN code (e.g. C10200 / Cu-OF, CW008A, or C80100 / Cu-C, CC040A for a dedicated cast spec)	Removes ambiguity between OFE, OFHC, ETP, and C80100, which share overlapping descriptions
Minimum conductivity	An explicit %IACS minimum matched to the grade, verified per ASTM B193	Turns the grade choice into a measurable, testable requirement rather than a name on a drawing
Hydrogen exposure requirement	State whether the part will be brazed, welded, or hydrogen-exposed downstream	Determines whether ETP is viable or an oxygen-free grade is mandatory
Material certificate	EN 10204 Type 3.1 with measured composition and conductivity from the production heat	Confirms the grade actually delivered matches the grade specified, not just the family name

Conductivity certification specifically - what verification protocol to ask for and what a proper material certificate should contain - is covered in full in conductivity certification for cast pure copper components.

Pahwa MetalTech selects and combines deoxidation practice based on the specific casting's application and required performance - a conductivity-critical bushing terminal and a general-purpose structural bracket don't get the same treatment, even in the same ETP heat. The result is tested on the finished part's actual conductivity, not assumed from what went into the melt. That's a deliberate difference from a one-size-fits-all deoxidation approach, which trades conductivity for porosity control across the board without the buyer ever seeing which one they got.

3 Signs Your High-Purity Copper Casting Was Misspecified or Poorly Made

• The drawing names a family, such as "oxygen-free copper" or "high conductivity copper," without a UNS or EN code, leaving the actual grade up to the foundry's interpretation.

  
  

• A part that will be brazed or welded downstream was specified in ETP copper without anyone checking whether that joining step introduces hydrogen exposure.

  
  

• The material certificate confirms composition but no measured conductivity value from the actual production heat - meaning the casting could still fail an IACS test despite a technically correct chemistry.

Source OFE, OFHC, ETP, and C80100 Copper Investment Castings

Pahwa MetalTech casts OFE, OFHC, and ETP copper as near-net-shape investment castings, verified to the conductivity and purity level each application actually requires - not just to a composition certificate.

As an OFHC casting manufacturer India relies on for transformer OEMs, GIS manufacturers, induction heating engineers, and green hydrogen developers alike, the grade and melting practice are matched to the actual service condition, not defaulted to whichever name sounds the most premium.

Share your drawing and application details through our contact page, and we'll confirm the right grade - OFE, OFHC, ETP, or C80100 - along with the verification protocol we'll test against before the first casting ships.