So, on the grade chart for tungsten copper, they're adjacent, and the paper difference works out to only 10 percent tungsten. In reality, that change results in changes in conductivity, hardness, density and cost, to a degree that will affect the rod's actual performance in the field. If you are quoting the same job for both parts and are not certain which to choose, it is simply a matter of which part of the application is more important: conductivity and machinability, or hardness and erosion resistance.
The following is an explanation of the difference between the two grades and how to decide on which ones to use when purchasing from a tungsten copper rod manufacturer.
The Core Trade-Off
Tungsten copper rod is not an alloy but is a composite material made up of particles of tungsten infiltrated with molten copper. The ratio of the two metals is what determines the grade and in turn, gives rise to a direct relationship: higher the ratio of tungsten, higher the grade, harder and denser the material; the more resistant to erosion, and less conductive and easier to machine. That is not correct; more copper results in the opposite. So it is that many consumers end up in the middle of the "general-purpose" range (between W70/Cu30 and W80/Cu20), deciding between the two a frequent one.
How the Two Grades Compare
The properties of W70/Cu30 are: density 13.80 g/cm³, hardness 175 HB, electrical resistivity 4.1 μΩ·cm, conductivity 42% IACS, bending strength 790 MPa. However, W80/Cu20 is significantly denser at 15.15 g/cm³, harder at 220 HB, less electrically conductive with a resistivity of 5.0 μΩ·cm (≈ 34% IACS), and more resistant to bending at 980 MPa. W70/Cu30 is also easier to machine as compared to W80/Cu20 which generally has a higher tungsten content and is therefore more expensive per kg.
What This Means in Practice
- Conductivity: W70/Cu30 has a significantly higher copper content which results in a higher electrical conductivity and thermal conductivity (approximately 42% IACS versus 34% IACS for W80/Cu20). It has an impact when the part requires efficient current flow or rapid heat dissipation.
- Hardness and strength: W80/Cu20 has a meaningful increase of hardness (220 HB vs 175 HB) and bend strength (980 MPa vs 790 MPa). This means directly increased resistance to deformation and wear under mechanical or thermal stress.
- Erosion resistance: W80/Cu20 has a longer service life than W70/Cu30 when used in high-energy discharge conditions due to its higher tungsten content, but with less conductivity.
- Machinability: W70/Cu30 is easier to machine and is, in general, the most forgiving grade to work with, which is a consideration when a part requires extensive post-processing after being supplied.
- Cost: Tungsten is the more expensive raw material of the two, so if the performance difference for your application is not critical, W80/Cu20 is likely to be more expensive than W70/Cu30 per kg, which should be considered.
When to Choose W70/Cu30
- Common use EDM electrode for die-sinking or mold cavity production.
- Applications where conductivity or heat dissipation matters as much as erosion resistance
- Parts requiring significant machining after the rod is supplied
- Cost-sensitive orders where W80/Cu20's extra erosion resistance isn't essential
When to Choose W80/Cu20
- Higher discharge energy or longer production runs without electrode dressing
- Applications where hardness and wear resistance take priority over conductivity
- Heavy-duty electrical contacts or components under sustained mechanical stress
- Situations where the extra cost is justified by extended service life
What to Check Before You Order
- Confirm the actual W/Cu ratio on your purchase order rather than relying on a generic "tungsten copper" spec — grade drives every property that matters to your application.
- Ask for a Material Test Certificate verifying composition and mechanical properties for the specific batch.
- Match the grade to your process conditions, not just habit — if you've always used W70/Cu30, it's worth checking whether your actual discharge energy or load conditions call for W80/Cu20 instead.
- Compare pricing per kg, since the cost difference between grades is real and should be weighed against the performance gap your application actually needs.
- Confirm the standard — ASTM B777 / ASME SB777 is the most widely referenced spec for tungsten copper rod and bar.
Conclusion
The materials W70/Cu30 and W80/Cu20 cannot be used interchangeably, as they occupy opposite ends of the same spectrum of electrical conductivity and erosion resistance. The material W70/Cu30 should be considered if electrical conductivity and machinability take precedence over hardness and wear resistance at higher discharge energy. At the same time, W80/Cu20 is preferable if hardness and wear resistance are the key factors.
FAQs
- Is W80/Cu20 always better than W70/Cu30?
No — "better" depends on the application. W80/Cu20 offers more hardness and erosion resistance, but W70/Cu30 offers better conductivity and easier machining. For general-purpose EDM work, W70/Cu30 is often the more practical and cost-effective choice.
- Which grade has better electrical conductivity, W70/Cu30 or W80/Cu20?
W70/Cu30 has better conductivity, at roughly 42% IACS compared to about 34% IACS for W80/Cu20, because of its higher copper content.
- Does W80/Cu20 last longer than W70/Cu30 in EDM applications?
In higher-energy discharge conditions, W80/Cu20's greater hardness and erosion resistance generally give it a longer service life before electrode dressing is needed, at the trade-off of reduced conductivity.
- Is W80/Cu20 more expensive than W70/Cu30?
Yes, typically. Tungsten is the costlier raw material of the two, so grades with higher tungsten content like W80/Cu20 generally carry a higher price per kg than W70/Cu30.
- Can I substitute W70/Cu30 for W80/Cu20 in an existing application?
It depends on what's driving the original spec. If the application relies on W80/Cu20's higher hardness or erosion resistance, substituting W70/Cu30 could shorten service life; if conductivity or machinability were the real priority, W70/Cu30 may actually be the better fit.