Chromium copper is the default electrode material in resistance welding — and for a lot of work, rightly so. But it has a failure ceiling, and every shop running coated steel, high electrode force, or long seam campaigns eventually finds it. Tungsten copper is what sits above that ceiling. This guide explains the trade in both directions and gives you the signals that it is time to switch.
Two different materials by design
Chromium copper (typically CuCr1Zr, RWMA Class 2) is a wrought copper alloy: copper strengthened by a small percentage of chromium and zirconium. Its great virtue is conductivity — typically in the 75–85% IACS range, several times better than tungsten copper. Its weakness is thermal: it is a precipitation-strengthened alloy, and the strengthening mechanism itself anneals away as the electrode face heats. Push it past its softening temperature — typically somewhere around 450–500 °C — and hardness falls off quickly.
Tungsten copper (W/Cu 75/25 or 70/30) is not a strengthened copper but a composite: a sintered tungsten skeleton infiltrated with copper. The skeleton does not soften in service; the composite retains useful hardness to roughly 900 °C. The price is conductivity — 38–45% IACS across our two grades — which means more of the weld heat is generated inside the electrode itself.
That single pair of numbers — conductivity versus softening — explains nearly everything in the table below.
Side-by-side
| Property (typical) | Chromium copper (Class 2) | W/Cu 75/25 | W/Cu 70/30 |
|---|---|---|---|
| Conductivity | ~75–85% IACS | ≥ 38% IACS | ≥ 42% IACS |
| Softening behaviour | Softens around 450–500 °C | Retains hardness to ~900 °C | Retains hardness to ~900 °C |
| Face wear mode | Mushrooms, picks up coating | Slow, even dressing | Slow, even dressing |
| Machinability | Easy, conventional | Hard bronze, carbide tooling | Hard bronze, carbide tooling |
| Relative cost per part | Low | Higher | Higher |
Figures for chromium copper are typical published ranges; confirm against your supplier’s certificate.
Where chromium copper is still right
- General spot welding on bare, low-carbon sheet at moderate force — the work never gets close to the softening limit.
- Schedules tuned around high secondary current where the electrode’s own resistivity is not the bottleneck.
- Any application where electrode cost dominates and consumption is already acceptable.
Changing material on a validated process costs qualification time. If your electrodes are not the problem, do not fix them.
Where tungsten copper wins
- Galvanized and coated steels. This is the classic trigger. Zinc alloys into a soft copper face, builds an insulating glaze, and forces dressing intervals to shrink. The harder CuW face resists pickup mechanically; the coating problem largely disappears. See seam welding wheel applications.
- High electrode force. On high-strength steels, force drives face growth on soft alloys. The 75/25 grade holds its face where Class 2 mushrooms. More on resistance welding electrodes.
- Seam welding wheels. A wheel conducts continuously for an entire coil run — cumulative heat is exactly what a precipitation-hardened alloy cannot survive. CuW wheels hold profile between dressings instead of growing and drifting.
- Flash and upset welding dies, where the die contact must not punch into the hot upset.
The signals that it is time to switch
- Dressing frequency is climbing on the same schedule and same steel — face glazing, not accident damage.
- Nugget or seam width drifts within a shift — the face is deforming between dressings.
- Electrode consumption doubled after a coating change — zinc pickup is eating a soft face.
- You are water-cooling aggressively and still losing tips — the alloy has passed its softening ceiling no matter how well you cool it.
The economics usually resolve simply: CuW costs more per piece and lasts multiples longer in exactly these conditions. The wider current window matters less than the wear arithmetic. If the comparison is close, run a trial on one station — sample quantities are small and lead times are short.
Common questions
Won’t the lower conductivity force me to a much hotter schedule? It runs somewhat hotter in the electrode and you compensate with current or time. In practice, shops switching to CuW for wear reasons end up net ahead, because the face stays metallic and the contact resistance stops wandering.
Can I mix the two on one line? Yes, and many do — chromium copper on benign stations, tungsten copper where the wear is. Alloy per station, schedule per alloy.
Which CuW grade for a first trial? Face wear and force problems point to W75Cu25; heat-limited schedules point to W70Cu30. The full trade-off is in our alloy selection guide.
Get a quote
If your line shows any of the switching signals above, send us the worn electrode or the drawing — request a quote and we will tell you plainly whether CuW is the right upgrade, with pricing valid 7 days and standard shapes shipping in 10–14 days, no minimum order.