Resistance welding electrodes are consumables, and the alloy you buy decides how they fail. The three families that dominate the market — chromium-zirconium copper, beryllium copper, and tungsten copper — are not interchangeable, but buyers are regularly asked to substitute one for another when lead times or prices move. This guide sets out where each alloy belongs, how it fails, and where the substitution boundary actually sits.
Chromium-zirconium copper (CuCr1Zr, RWMA Class 2)
The default electrode material and the right one for a large share of work. Typically around 80% IACS conductivity with moderate hardness, it carries heavy current with little resistive loss and machines like ordinary alloy steel.
- Best for: general spot welding of bare low-carbon steel, large electrodes where current demand is high, holders and shanks.
- How it fails: face mushrooming under electrode force, and — decisively — zinc pickup on galvanized or coated sheet. The soft copper face alloys with the coating, builds an insulating glaze, and forces early dressing.
- Substitute for W/Cu? On bare, thin, low-force work, yes and often cheaper. On coated strip or high-force schedules, no: the glazing and mushrooming that W/Cu resists are exactly its failure modes.
Beryllium copper (RWMA Class 3/4)
Harder than CrZr (typically up to around 100 HRB in the harder tempers) with conductivity typically in the 22–45% IACS range depending on class. Its strength is mechanical: it holds shape and resists deformation where softer copper alloys indent.
- Best for: current-carrying structural components — holders, fixtures, shafts, projection-welding die bodies — where strength matters as much as conduction.
- How it fails: on weld faces, the same coating-pickup and wear problems as other copper alloys, at higher material cost.
- One caution for buyers: beryllium in dust form is a serious occupational health hazard, so machining BeCu in-house carries obligations that W/Cu and CrZr do not. The beryllium copper comparison prices that risk into the decision.
- Substitute for W/Cu? As a die or holder body, sometimes yes. As a weld face on coated or high-strength steel, it buys you hardness without escaping the copper-face failure modes.
Tungsten copper (W/Cu 75/25 and 70/30, RWMA Class 10/11)
A different construction entirely: a sintered tungsten skeleton infiltrated with copper. The tungsten carries mechanical load and resists erosion; the copper carries current. Typically 38–42% IACS and 80–95 HRB depending on grade — less conductive than CrZr, harder than both copper alloys.
- Best for: seam welding wheels on long campaigns, coated and galvanized strip, high-strength steels under high electrode force, projection-welding facings, and anywhere dressing frequency or profile drift — not raw current capacity — limits production.
- How it fails: slowly and evenly. The tungsten skeleton changes the wear mode from smearing and glazing to gradual, predictable dressing, which is what makes reorder cycles plannable.
- The cost: conductivity. A schedule tuned for CrZr may need more current on W/Cu, which is why the 70/30 grade exists — roughly 25% more conductive than 75/25, at the cost of some wear life.
The substitution boundary, plainly
Running substitution both ways:
- W/Cu replacing CrZr or BeCu: works whenever the failure mode is face wear, glazing, sticking or profile drift — the majority of coated-steel and long-campaign problems. Expect to retune the weld schedule upward on current; W/Cu is less conductive.
- CrZr replacing W/Cu: only sensible on bare, thin, low-force work where conductivity is the binding constraint and electrode life is already adequate. On coated strip, expect dress frequency to multiply — the chromium copper comparison draws that line case by case.
- Within W/Cu: 75/25 for wear-limited stations, 70/30 for heat-limited ones. Both grades machine and fit identically, so switching is a purchasing decision, not a process change.
One caution applies to any substitution: weld schedules are tuned to the alloy in the drawing. If you replace an existing electrode, match the specified alloy unless you can run a controlled trial — samples are cheap and typically ship in 10 days or less.
Get the right alloy for your schedule
ArcTung manufactures W/Cu 75/25 and 70/30 electrode wheels, threaded electrodes, rods and blocks at its Heyuan factory — no MOQ, standard shapes in 10–14 days, FOB Shenzhen/Nansha. Send your weld schedule and part to sales@arctung.com and we will tell you whether tungsten copper is actually the right answer.