Figure 1: An example of a graphite electrode.
Figure 6: Copper also can be used for photo engraving and acid etching.
Figure 2: Some new high-speed mills are specially designed to machine graphite - and can even cut square internal corners.
Figure 3: The finish on the graphite should be as good as you need in the mold.
Figure 5: Copper can be used for coining and forging.
Figure 4: Copper is useful in small cavities, where it is difficult to polish.
When it comes time to decide whether to use graphite or copper electrodes in your shop, it's important to look at the big picture. According to Stu Haley, regional manager of Belmont Technologies, Inc., a provider of EDM supplies, tooling, accessories and machines, "To say which electrode works best is very difficult, it is totally applications driven. So much depends on what you have to work with on your shop floor in the way of support equipment. Both copper and graphite provide approximately the same end result. The difference is time to EDM the work and electrode manufacturing time and cost."
Haley explains that choosing an electrode material is often a result of where you were born and what type of EDM equipment you use. "For example, graphite was basically developed in the United States back in the early s, so the American EDM equipment manufacturers in those days concentrated on the graphite circuitry when designing their equipment," he says. "Whereas, since the European and Asian EDM equipment manufacturers didn't have access to graphite, they developed copper circuitry.
"If you have newer equipment built after , the electrode material of choice in North America is graphite," he adds. "This is used in 90% of the applications. In Europe and Asia, graphite is becoming more popular as an electrode material because of availability, machinability and speed of cutting."
Following are some of the advantages and disadvantages of each material so that you can decide which is best for your application.
Sold by grades, graphite cuts approximately three times faster than copper, according to Haley. "What makes a good grade or a poor grade is particle size," he explains. "Particle size gives you strength, machinability and greatly influences the metal removal rate, wear and the surface finish. Graphite is made up of carbon particles that are put through a graphitizing process to produce graphite. The smaller the particle size is, the better the graphite. Particle sizes in different grades of graphite can be ." for general-purpose use to ." for the extremely fine detail and superior surface finishes. Graphite can be purchased in big blocks, and then cut up to be machined; or it can be ordered precut or ground into the size you require.
"Graphite machines very easily — you can mill it, grind it, turn it, drill it, tap it, even file it to whatever shape you want," Haley continues. "Another advantage of graphite is that it doesn't burr. You can put it on a duplicating machine or a graphite high-speed mill and cut out complex shapes and forms, and once it's cut you are finished — with no deburring." (See Figure 1)
Additionally, graphite's high melting temperature results in less wear than other electrode materials, so a mold could be cut with one or two electrodes on a CNC EDM machine with very little wear, Haley adds. "A CNC sinker may need a third or forth electrode to finish the mold," he notes. "It depends on the age of the EDM machines."
If your shop has older fabricating equipment, machining graphite electrodes will result in dust particles on the shop floor and in the nearby machines. However, the new high-speed mills that are sold today are specially designed to machine graphite. "They are totally enclosed and have a vacuum system to remove all of the dust," Haley points out, "and there are some machines that can even cut square internal corners." (See Figure 2)
Another important point to keep in mind is that the finish on any electrode is the finish that will be put in the mold. "So, if you have a lot of cutter or grinding marks on the electrode, you will reproduce that in your mold," Haley says. "Normally, the finish on the graphite should be as good as you need in the mold."
Haley notes that copper can be cut on wire EDM machines, but there are only certain graphites that can be cut on a wire machine — the particle size should be five microns or less. Copper also is a little more forgiving in a poor flush situation than graphite. "In EDM, if the flush doesn't remove the eroded particles or chips out of the cutting area, there's something that can occur where you get a non-pulsating, direct flow of current from the electrode to the workpiece," Haley explains. "The result of this is a pit in the workpiece. Copper is more forgiving in those applications — all metallic electrodes are — they won't arc out as fast. But some of the newer EDM power supplies have adaptive logic or fuzzy logic, which eliminates the problem altogether. Copper — when used at specific settings with the correct flushing techniques using a CNC machine or a machine with an orbiting system — can produce a mirror-like surface finish. This is useful in small cavities where it is difficult to polish."
When you add tungsten to copper (copper tungsten), the result is an electrode material that has extremely good wear characteristics but is very difficult to machine, Haley notes. "When EDM'ing carbide, this is the best metallic electrode material to use. The best graphite material would be copper graphite, which is graphite impregnated with copper," he says.
According to Haley, there are alternative ways of machining copper — including coining (see Figure 5), forging, photo engraving/acid etching (see Figure 6) and stamping/forming. There are some shops that make a form and then copper plate it.
"Copper is more difficult to machine," Haley says, "and when you mill it, it has the tendency to stick to the cutter. When you grind it, it can clog up the grinding wheel. It heats up quickly and has a tendency to grab the grinding wheel. You'll have burrs no matter how you machine it, so you have to deburr it. Size and weight also can be an issue. A 12" x 7" x 2 3/4" piece of copper weighs 75 pounds, whereas a piece of graphite the same size is 11 pounds.
"The bottom line is use what you think will work best in your shop with the equipment that you have available," Haley continues. "If some electrodes are beyond your machining ability, have someone make them for you. You have to base it on your own experience and the resources you have available. Ask for suggestions from the equipment manufacturer or from your electrode material supplier. Regardless of what electrode material or combination of materials you decide on, be sure that you know the speeds and feeds to machine the material safely. When in doubt, ask."
Graphite is ideal for EDM electrodes due to its excellent thermal resistivity and many other properties. Graphite electrodes have a very high melting point. These are not only efficient and resistant to corrosion but are also much easier to use and maintain. This makes them perfect for applications such as die, mold, robotic systems, etc. Graphite has a layered structure and the layers are bound by weak Van der Waals forces. This makes graphite electrodes an excellent conductor of electricity. And allow uniform distribution of electricity during the machining process. It results in accuracy in the separation process. Additionally, these are durable and can withstand repeated use over time. This makes them a cost-effective choice.
· It is durable and does not corrode in contact with water
· It is able to conduct electricity and last for a long time
· Additionally, graphite is a good choice for electrodes to be used in several industries due to its low cost and plenty in nature
· Graphite is also non-toxic and eco friendly
· Graphite is easy to work with and can be cut and shaped into any desired shape.
Graphite electrodes might sound complicated, but simply put, they are rods made of graphite used to conduct electricity in industrial processes like steelmaking.
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Graphite can withstand extremely high temperatures, so it’s perfect for generating the intense heat needed to melt metal and make steel.
Synthetic graphite (rounds, rods and blocks)
Electrode Grade (electrodes, blocks, plates)
Medium Grain (~.030” Grain size)
Fine Grain (~.008” Grain size)
Super Fine Grain (5 micron grain size)
Anti-Oxidation treated
Phenolic impregnated
Metal impregnated
Purified (pure to 5 ppm)
Graphite tubes (all grain sizes)
Graphite dust and chunks
Carbon (rounds and blocks)
Carbon composites (chopped fiber, long strand, 3D and 4D woven)
Graphite and carbon felts
Graphite and carbon insulation
Graphite foil
Treated and non-treated flux tubes
Porous graphite and carbon
The main ingredient in graphite electrodes is synthetic graphite, which is produced by heating petroleum coke, a by-product from oil refining. This transforms the coke into a very crystalline, conductive form of carbon.
The electrodes also contain elements like coal tar pitch and calcined anthracite to help hold them together and resist oxidation while being baked at blazing temps over °C. Some metal particles are added, too, to boost conductivity.
In steel mills, graphite electrodes make melting scrap metal and raw materials possible by creating electrical arcs that heat up to about °C. This allows the desired chemical transformations to occur so the end product steel has just the right composition and properties.
The electrodes withstand incredibly high heat and current loads as they constantly burn away and get replaced in the furnace. Good-quality electrodes are vital for steel mills to operate efficiently.
Frequently Asked Questions
Steel may be the biggest user, but graphite electrodes wear many hats. In smelting processes for metals like titanium and copper, these electrodes can carry massive currents in submerged arc furnaces while resisting damage from extreme conditions.
They also help produce phosphorus, carbides, zinc, and other non-ferrous metals. Even diamond production relies on the unique merits of graphite electrodes.
Beyond heavy industry, graphite electrodes also serve some very specialized commercial roles. For instance, in electrical discharge machining (EDM), graphite contacts carefully shape metal parts using controlled electrical sparks. EDM is used to cut complicated shapes that would be impossible with conventional tools.
Graphite contacts are also found in electrical probes for measuring surface temperatures during welding or heat treatment. Even your everyday spot welder relies on graphite!
Hardworking electrodes operate in scorching, harsh environments, so it’s crucial not to neglect maintenance. Electrodes need to be regularly inspected for cracks or oxidation. Any damage should be repaired immediately with special conductive filler materials or re-shaping.
Proper storage and handling prevent issues down the line. Correctly maintained electrodes will keep working reliably for you over the long haul.
Reclaimed graphite electrodes can be repaired and reused, which improves sustainability without sacrificing performance. Repaired electrodes are ideal for industrial applications and can offer substantial cost benefits.
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Look inside any major steel mill or metal smelter globally, and you’ll find graphite electrodes hard at work. Even with technological advancements, graphite electrodes have been indispensable in these types of facilities for years.
Graphite electrode technology has come a long way from the early days. Modern ultra-high power (UHP) electrodes allow steel mills to operate faster and more efficiently.
Ongoing improvements like enhanced thermal properties and strength through nanomaterials point toward even better electrode performance in the future.
Advantages of Graphite
We can machine the largest parts in the industry with capabilities that include 4th and 5th axis milling, sanding, grinding, coring and drilling.
We provide in-house programming and drawing capabilities with both NX and Solid Edge software.
In addition to worldwide access to all graphite manufacturers, we offer a diverse graphite inventory of certifiable, extruded, molded and isostatic molded material giving you fast turnaround time.
We can repair graphite electrodes for steel mills and other industrial applications for a fraction of the cost of machining new ones.
Sticking to the principle of "Super Quality, Satisfactory service" ,We are striving to be a good business partner of you for UHP, HP, RP Grade Graphite Electrodes
The company is the world’s best Antioxidant Graphite Electrode supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.