Electric Arc Furnace (EAF) Solutions
Graphite electrodes are used mainly in electric arc furnace steel production. They are presently the only products available that have both high levels of electrical conductivity and the capability of sustaining the extreme heat generated in this demanding environment. Graphite electrodes are also used to refine steel in ladle furnaces and in other smelting processes. GrafTech currently offers several grades of graphite electrodes to choose from:
UCAR® Grade AGX™ Graphite Electrodes – A premium grade recommended for high power, ultra-high power and DC furnaces operating under severe electrical and/or mechanical conditions. AGX electrodes are also recommended for more demanding ladle furnace applications because of its increased current-carrying capacity.
UCAR® Grade ALX™ Graphite Electrodes – An ultra-high power grade addressing AC and DC applications where stub losses and column breakage is an issue.
UCAR® Grade LFX™ Graphite Electrodes – A premium grade recommended for ladle furnaces or for low-power melting applications where standard electrodes fail to perform. The charts on this page (for melting furnaces and ladle furnaces) are based on the heating effect in a graphite electrode column by applying an assumed average phase current.
To learn more:
The ArchiTech™ Furance Productivity System is a 24/7/365 advanced high-speed EAF diagnostic, analysis and reporting system proven to reduce cost, increase productivity, and help maintain uninterrupted flow.
With more than 150 installations in 25 countries, what are the possibilities for your shop?
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What are Graphite Electrodes?
OK. What is an Electric Arc Furnace?
An electric arc furnace is essentially a big recycling machine. Simply put, it’s a large pot into which scrap steel, like old cars, bicycles, and refrigerators, are dumped. The furnace operator loads (called charging the furnace) carefully screened and selected scrap steel into this big pot. Then, the operator swings the furnace roof back over the pot and lowers it into place.
The electrodes are part of the furnace roof structure. Electrodes can be small, 75 millimeters (3 inches) in diameter, or quite large, up to 800 millimeters (32 inches) in diameter and as much as 3400 millimeters long. The largest weigh more than two metric tons (4,400 lbs.). The manufacturer of the furnace determines the size the electrode should be.
The electrodes are assembled into columns, usually 3 to a column. Graphite connecting pins-tapered and threaded on each end screw two electrodes together. Some furnace operators assemble the columns on the shop floor and lift them into place whole. Others add electrodes one at a time to the top of the column while it is still on the furnace. Each electrode column has a large steel arm which moves it up and down.
Furnaces using 3-phase AC (alternating current) electricity have 3 electrode columns; DC (direct current) furnaces only need one column of electrodes, but they are generally larger in diameter as they are responsible for handling more electrical power.
Once the furnace roof is in place, the electrodes are lowered until the tip of the electrode column almost touches the top of the scrap pile. Huge amounts of electricity–large furnaces use enough electricity for a town of 40,000 people–flow through large water-cooled cables into the electrodes. At the bottom of the electrode column, the electricity jumps (or arcs) from the electrode tip to the nearest piece of steel scrap. The intense heat of this electric arc melts the steel scrap, hence the name of the electric arc furnace.
The tip of the electrode will reach 3,000 degrees Celsius or 5,000 degrees Fahrenheit, half the temperature of the surface of the sun. Electrodes are made of graphite because only graphite can handle the necessary electrical power, while withstanding this incredible temperature.
Eventually, all the steel is melted. The furnace operator turns off the power and raises the electrode columns. The furnace is then tipped on its side to pour the molten steel into giant buckets called ladles. The ladles quickly carry the molten steel downstream to a Ladle Treatment Station (LMF) for further chemical processing or directly to the steel mill’s caster, which is the next step in making new and useful product from recycled steel scrap.
To answer the question, then, what is a graphite electrode? A graphite electrode is a device to conduct electricity down into an electric arc furnace which generates sufficient heat to melt steel scrap.
Making a UCAR® Graphite Electrode
Premium quality calcined petroleum coke is crushed, screened, and hot-blended with pitch in controlled proportions. The resulting plastic mass is extruded through a forming press and cut into specified lengths, the so-called ‘green’ electrodes, before being water-cooled in a temperature controlled bath.
Green electrodes are placed in large cans called saggers (pronounced say gers) and baked to over 800° C (1400° F) in specially designed, computer-controlled furnaces. It takes 1-to-2 weeks to carbonize the pitch depending upon the size of the electrodes being made. After cooling, the baked electrodes made of amorphous carbon are cleaned, inspected, and sample-tested.
Next, the baked electrodes are impregnated with a special pitch to give them the higher density, mechanical strength, and electrical conductivity they will need to withstand the severe operating conditions inside our customers’ electric arc furnaces.
A second baking cycle, or “rebake,” is required to carbonize the pitch from impregnation and to drive off any remaining volatiles. Rebake temperatures reach almost 750°C (1300° F).
The rebaked carbon electrodes are further processed in long electric resistance furnaces. Laid end-to-end, or “longitudinally,” the electrodes are heated to over 3000° C (5000° F). This ultra high temperature restructures the carbon to its crystalline form—graphite. Then the electrodes are once again cooled, cleaned, inspected, and sample-tested under GrafTech’s rigorous control procedures.
In Machining, the electrodes outer diameter are turned to its finished dimension. The two end faces are also machined to tolerance and given threaded sockets. The sockets accept GrafTech’s double-tapered, machine-threaded graphite connecting pins which allow our customers to join electrodes together into columns.
After machining, the finished graphite electrodes are inspected, protectively capped and palletized. Each electrode prominently displays the GrafTech™ UCAR® Graphite Electrode logo as it is sent on its way to our customers.
Choosing the Right Electrode
Selecting the Proper UCAR® Electrode Grade
UCAR® Grade AGX™ Graphite Electrode – A premium grade recommended for high power, ultra-high power and DC furnaces operating under severe electrical and/or mechanical conditions. AGX is graphite electrodes are also recommended for more demanding ladle furnace applications because of its increased current-carrying capacity.
UCAR® Grade ALX™ Graphite Electrode – An ultra-high power grade addressing AC and DC applications where stub losses and column breakage is an issue.
UCAR® Grade LFX™ Graphite Electrode – A premium grade recommended for ladle furnaces or for low-power melting applications where standard electrodes fail to perform. The charts on this page (for melting furnaces and ladle furnaces) are based on the heating effect in a graphite electrode column by applying an assumed average phase current.
Size and Grade Selection
To properly select the right UCAR® graphite electrode for your application, always consider the following operating characteristics of your furnace:
- Conversion cost
- Steel type and grade
- Electrode consumption goal
- Refractory consumption goal
- Productivity goal
- Electrode strength and oxidation
- Furnace design
- Scrap types/charging practice
- Burner/oxygen usage
- Water spray rings
- Fume control system
- Power level & power input program meltdown/refine
- Tap-to-tap time
- Slag practice
Depend on GrafTech
GrafTech’s global production network provides customers with a reliable supply of quality UCAR® Graphite Electrodes.
Around the world, GrafTech works closely with trucking companies that understand delivery requirements and provide timely, reliable service at a competitive price. We also work with ocean carriers that have the specialized equipment required for secure transport of our graphite electrodes and frequent sailing schedules to multiple destinations.
Together, we meet customers’ schedules and deliver on time, 99% of the time.
World Class Technical Service
We demonstrate it to our customers every day. GrafTech fully understands the electric furnace steelmaking process and applies that understanding in helping customers optimize their melting operations. Using the latest analytical technologies, GrafTech focuses on the steelmaker’s ability to operate more efficiently and profitably.
Benefiting from more than a century of experience around the world, GrafTech has built a solid reputation for practical solutions. Our engineers and technicians work side-by-side with furnace operators making first-hand observations, recommending improvements and recording results.
Bringing State-of-the-Art, Real-Time Analysis to your Shop
- Oxygen usage
- Electrode consumption
- Furnace regulation
- Optimum power profile
- Power-on time
- Time utilization
- Maximum productivity
Our exclusive analytical programs and ArchiTech Productivity System, combined with our recognized expertise in analysis, encompass the total arc furnace environment. This thorough furnace monitoring capability, whether in-shop or remotely from our technical facilities, allows us to help our customers (1) optimize power input to their furnaces, (2) reduce process variation, and (3) increase productivity. This analytical ability enables GrafTech professionals to define and completely understand the operating parameters of the electric arc furnace.
Only from such a comprehensive assessment can practical solutions be developed.
Our proven problem solving methodology covers the broad spectrum of electric furnace steelmaking: from furnace design criteria to graphite electrode applications; from charge to liquid steel.
Bringing Valuable, Customized Training Programs to your People
- Global steelmaking
- Benchmarking steelmaking
- Technology-focused seminars
- New Furnace start-up seminars
- Technology leadership
- Electrode handling
Just as we do in our manufacturing operations, GrafTech strives for continuous improvement in the steelmaker’s operations. We apply our extensive expertise in Total Quality Management systems to all analytical efforts. Taken as a whole, our capabilities, experience, and global presence enable you to learn state-of-the-art techniques from around the world.
Value Added Services
The World’s Leading Electrode and Service Provider
- More than 130 years of carbon and graphite material science expertise
- Global Customer Technical Service (CTS) expertise
- World class research & development
- Multiple plant sourcing capability
- Product optimization & testing capability
- Electrode recovery assistance
- Electrode inventory management
- Industry leading safety practices
UCAR® Arc Furnace Electrode Digest©
At your disposal, GrafTech offers the UCAR® Electric Arc Furnace Electrode Digest – the classic melt shop primer. This includes twelve in-depth chapters covering The Evolution of Arc Furnaces, Furnace Regulation, Foamy Slag, Post Combustion, and more that were more recently added to the original version. This modern edition takes furnace operators and melt shop managers to the next level of educational excellence addressing the physics, chemistry, and engineering aspects of electric furnace fundamentals.
This digest is distributed exclusively through GrafTech representatives. To request your copy, please reach out to your local GrafTech representative or contact us today.
Optimization of Electrode Performance
Monitoring and analysis of factors affecting electrode performance.
- Handling Practices
- Jointing Techniques
- Time Utilization
- Oxygen and Burners
- Foaming Slag
- Furnace Regulation
- Power Program
- Raw Materials
- Electrode handling
- Modes of consumption
- EAF benchmarking
- EAF productivity
- Total energy utilization
- Ladle furnace operations
- Electrical priciples
- Chemistry energy
- EAF raw material
- Oxygen practices
- Inventory management
- Slag practices
Our global presence gives us an independent overview of all EAF equipment and technology. We can help you in your new project planning and furnace start-up.
- Equipment Selection
- Productivity planning and capability
- Configuration and vetting
- GrafTech published papers
- Papers published by other experts
- Customized information search
Arc Furnace Monitoring
Using the web-based ArchiTech™ Furnace Productivity System and other latest technology, arc furnace electrical operation can be analyzed and optimized.
- Evaluate and trend electrode consumption by phase
- Maximize power input by determining effectiveness of power profile
- Determine electrical balance and solve arc flare problems
- Enhance foaming slag practice
- Trend more than 75 furnace parameters, including those affecting electrode consumption
- Power input optimization
- Primary and secondary metering, as well as phase sequence verification
- Regulator response and interaction analysis
- Calculate short circuit reactance, line reactance, and other key parameters
- Mobile platform
- Surface hidden problems with statistical based alerts
EAF Steel Practices
Through our close and confidential relationship with customers operating more than 2,000 electric arc furnaces in more than 80 countries, we have an unparalleled view of arc furnace performance.
- Comparative analysis through benchmarking
- Advice and Training on best practices
New Arc Furnace Technology
Through our extensive technical contact with the steelmaking community, we are current of all the latest steel technology trends. GrafTech experts can help in understanding the implication of these developments.
Arc Furnace Technology Seminars
We tailor seminars for customer groups focusing on subject areas of interest. This list is only a sampling of subjects we have addressed in the past:
- EAF benchmarking
- AC/DC furnace comparisons
- High reactance technology
- Physics of arcs
- Current EAF technologies
- Electrode consumption model
- Worldwide raw material trends
UCAR® graphite electrodes are covered by one or more of the following U.S. patents: US6440563; US6280663; US6803108. Other U.S. and foreign patents granted or pending.
The UCAR® ALX™ graphite electrodes are covered by one or more of the following U.S. and foreign patents: CN ZL200580020188.5; EP1813134; KR 10-1009569; KR 10-1049641; MX 260540; PL 210593; RU 2369047; US7230969; US7016394; US7301982; US 9313834. Other U.S. and foreign patents granted or pending.
UCAR® graphite electrodes may also be covered by one or more of the following patents: European Patent No. CA 2401625; EP1261549; KR 802030; MX 248543 as well as EP 1993325 and EP 2373121
Customer Technical Services has obtained the following proprietary rights regarding their service offerings: CA2392788; CA 2528151; EP 1327352; MX 229069; US 6804582; US 7386369
The ArchiTech® Furnace Monitoring System may be covered by one of more of the following patents: EP 1817943; EP 2776770; EP2928268; US 7313160; US 7991039; US 9439247; D749621