What your Graphite Electrode supplier does NOT tell you

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Dear Graphite Electrode User, 

Have you ever asked yourself the following question:

How can electrode manufacturers still cover costs in times of rising petroleum needle coke prices and decreasing graphite electrode market prices?

When you suspect your manufacturer is already producing below cost, you may become a little bit cautious. 

Especialy, at this time of market crisis, you want to know if your electrodes are really genuine HP or UHP quality.

Why?

Well, as you may know, graphite electrode market prices depend on large on petroleum coke costs.

Therefore, the higher the petreleum coke market prices, the lower the margin of the manufacturer. And the higher your risk the supplier reduces the needle coke content in his recipe.

Also, as a steel mill or foundry, you have to deal with the threat of price increases in energy costs and the never-ending fulfillment of all possible environmental regulations.

And you definitely don’t want to have to deal with unforeseeable costs in your production that come from changing electrode consumption.

This is why you want to know if your electrodes are really genuine HP or even UHP grades.

You see, I would never say

“your supplier is lying to you or he would hide important info.”

But if you have already made the following annoying experience, you may get a little bit suspicious:

Your electrode consumption has fluctuated … Although you have always ordered “the same quality“according to your supplier?! 

Wouldn’t you agree that you must know the differences between electrode grades?

But is there no way for you to inform yourself about graphite electrodes?

From websites, from your supplier brochures or scientific papers not really.

Electrode buyers have a hard time finding facts about raw materials used, target performances and production technology

Because apart from a few hard-to-understand scientific reports, there is simply not enough content out there. Even a time-consuming Internet research will give you little clues.

Try a google-search for “graphite electrode grades” and you will see advertisements after advertisement by electrode vendors – in Germany, that is nearly 3 pages full of ads.

And if you do find something valuable, that may be a book about Material Science that has a small 100 words section about graphite electrodes. However, you may notice that the section is about a different kind of electrodes, not the one you are using for your electric arc furnace.

It is hard to find facts about electrodes on your own

also in part because many electrode vendors don’t want to educate their customers.

What I mean is this:

If you feel that your electrode consumption is too high – you would probably ask your trusted supplier for help.

You want a professional and partnership-based discussion of all possible reasons for the failure AND get a small lecture in graphite electrode technology.

Then it is more than annoying to hear as an answer from your supplier:

“The increased electrode consumption can be subject to a host of factors …” without being any concrete.

A pretty simple way to deny responsibility, right? And while it is true that consumption can come from many factors, it is pretty cumbersome to feel not being taken serious.

I would certainly understand if this kind memory makes you angry.

OK, so next I’ll tell you something that will excite you.

There is now a bundle of  whitepapers 

with all the essential knowledge you will ever need in your EAF carreer

It is called The First Ever “Library of Graphite Electrodes” that consists of 4 whitepapers. 

Each whitepaper is between 6 and 25 pages long and you will learn in understandable language:

  • the actual difference between electrode qualities in understandable language
  • how to see differences between the qualities, performance and resistivities
  • the raw materials that determine fully 80 % of your purchasing costs
  • production methods and technologies
  • what it means to speak the language of your electrode suppliers 
  • how to recognize when the actual performance deviates from the data sheet

Within only 20 minutes reading time a day you will learn all there is to it. The info is demonstrated on clear charts and graphs and understandable, no tech-language.

This means you or your colleagues will only everything there is to know about graphite electrodes with only a small investment of your time and effort.

The bundle of booklets has been used by various steel producers to educate their purchasing managers and EAF engineers. 

In the fastest time possible, you will learn everything there is to know about graphite electrodes and you will immediately recognize when your supplier is trying to trick you!

The bundle was sold in print or electronic PDF for €69 during the electrode crisis in 2017 to over 70 steel mills in Europe and the EMEA region

Now, for a short time and only on this blog, the bundle is available for FREE and immediate download. 

The knowledge comes from 61 years of experience in buying, using electrodes and sharing ideas with graphite electrode users in 35 countries.

Download your ebook today and never be speechless again in front of your supplier.

Click here to learn more

(Only for a limited time!)

All-weather solar cells: everything is possible

Never before have the topics of climate protection and renewable energies attracted as much media attention as these days. The rethinking in society begins and drives the energy transition and the development of progressive innovations.

Until now, Chinese scientists have developed solar cells that take advantage of the sun and water to a certain extent, and which generate energy not only from solar power as before, but also from raindrops – and that even at night.

Continue reading All-weather solar cells: everything is possible

Solar energy is booming! Here are the latest developments of the industry

Solar energy is booming! Here are the latest developments of the industry

The future belongs to solar power. Renewable energies are not only on everyone’s lips, electricity generated from solar power, among other things, is becoming increasingly cheaper and more efficient.

The day when photovoltaics and solar thermal technology replace fossil fuels such as coal, gas and oil is getting closer.

This positive trend also inspires many creative minds to deal with solar energy in order to further exploit the enormous potential.

Continue reading Solar energy is booming! Here are the latest developments of the industry

The Electric Arc Furnace (part 5) – Construction

This is the fifth and last part of our depiction of EAF steelmaking.

Construction

Main components are furnace shell with its tapping spout, or more common nowadays, its eccentric bottom taphole (EBT) and its working/slag opening (slag door) the removable roof, the water cooled wall panels, the electrodes with the electrode support arms and the other electricity-conducting elements

An electric arc furnace used for steelmaking consists of a refractory-lined vessel, usually water-cooled in larger sizes, covered with a retractable roof, and through which one or more graphite electrodes enter the furnace.[6]

The furnace is primarily split into three sections:

  • the shell, which consists of the sidewalls and lower steel “bowl”;
  • the hearth, which consists of the refractory that lines the lower bowl;
  • the roof, which may be refractory-lined or water-cooled, and can be shaped as a section of a sphere, or as a frustum (conical section). The roof also supports the refractory delta in its centre, through which one or more graphite electrodes enter.

Electric_Arc_Furnace_construction
A schematic cross-section through an EAF. Three electrodes (yellow), molten bath (gold), tapping spout at left, refractory brick movable roof, brick shell, and a refractory-lined bowl-shaped hearth.

The hearth may be hemispherical in shape, or in an eccentric bottom tapping furnace (see below), the hearth has the shape of a halved egg. In modern meltshops, the furnace is often raised off the ground floor, so that ladles and slag pots can easily be maneuvered under either end of the furnace.

Separate from the furnace structure is the electrode support and electrical system, and the tilting platform on which the furnace rests. Two configurations are possible: the electrode supports and the roof tilt with the furnace, or are fixed to the raised platform.

A typical alternating current furnace is powered by a three-phase electrical supply and therefore has three electrodes.[7] Electrodes are round in section, and typically in segments with threaded couplings, so that as the electrodes wear, new segments can be added.

The arc forms between the charged material and the electrode, the charge is heated both by current passing through the charge and by the radiant energy evolved by the arc. The electric arc temperature reaches around 3000 °C (5000 °F), thus causing the lower sections of the electrodes to glow incandescently when in operation.[8]

The electrodes are automatically raised and lowered by a positioning system, which may use either electric winch hoists or hydraulic cylinders. The regulating system maintains approximately constant current and power input during the melting of the charge, even though scrap may move under the electrodes as it melts.

The mast arms holding the electrodes can either carry heavy busbars (which may be hollow water-cooled copper pipes carrying current to the electrode clamps) or be “hot arms”, where the whole arm carries the current, increasing efficiency.

Hot arms can be made from copper-clad steel or aluminium. Large water-cooled cables connect the bus tubes or arms with the transformer located adjacent to the furnace. The transformer is installed in a vault and is water-cooled. [6]

The furnace is built on a tilting platform so that the liquid steel can be poured into another vessel for transport. The operation of tilting the furnace to pour molten steel is called “tapping”.

Originally, all steelmaking furnaces had a tapping spout closed with refractory that washed out when the furnace was tilted, but often modern furnaces have an eccentric bottom tap-hole (EBT) to reduce inclusion of nitrogen and slag in the liquid steel.

These furnaces have a taphole that passes vertically through the hearth and shell, and is set off-centre in the narrow “nose” of the egg-shaped hearth. It is filled with refractory sand, such as olivine, when it is closed off.

Modern plants may have two shells with a single set of electrodes that can be transferred between the two; one shell preheats scrap while the other shell is utilised for meltdown. Other DC-based furnaces have a similar arrangement, but have electrodes for each shell and one set of electronics.

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The Electric Arc Furnace – Part 4 (EAF vs the others)

This is the fourth part of our EAF-series. It is about the differences and communalities of EAF, Indiction Furnaces, Ladle furnaces, Plasma Furnaces & Vacuum Arc Furnaces.

EAF vs other electrical furnaces

Arc furnaces differ from induction furnaces in that the charge material is directly exposed to an electric arc and the current in the furnace terminals passes through the charged material.

For steelmaking, direct current (DC) arc furnaces are used, with a single electrode in the roof and the current return through a conductive bottom lining or conductive pins in the base.

The advantage of DC is lower electrode consumption per ton of steel produced, since only one electrode is used, as well as less electrical harmonics and other similar problems.

The size of DC arc furnaces is limited by the current carrying capacity of available electrodes, and the maximum allowable voltage. Maintenance of the conductive furnace hearth is a bottleneck in extended operation of a DC arc furnace.

In a steel plant, a ladle furnace (LF) is used to maintain the temperature of liquid steel during processing after tapping from EAF or to change the alloy composition. The ladle is used for the first purpose when there is a delay later in the steelmaking process.

The ladle furnace consists of a refractory roof, a heating system, and, when applicable, a provision for injecting argon gas into the bottom of the melt for stirring. Unlike a scrap melting furnace, a ladle furnace does not have a tilting or scrap charging mechanism.[citation needed]

Electric arc furnaces are also used for production of calcium carbideferroalloys and other non-ferrous alloys, and for production of phosphorus. Furnaces for these services are physically different from steel-making furnaces and may operate on a continuous, rather than batch, basis.

Continuous process furnaces may also use paste-type, Søderberg electrodes to prevent interruptions due to electrode changes. Such a furnace is known as a submerged arc furnace because the electrode tips are buried in the slag/charge, and arcing occurs through the slag, between the matte and the electrode. A steelmaking arc furnace, by comparison, arcs in the open.

The key is the electrical resistance, which is what generates the heat required: the resistance in a steelmaking furnace is the atmosphere, while in a submerged-arc furnace the slag or charge forms the resistance. The liquid metal formed in either furnace is too conductive to form an effective heat-generating resistance.

Amateurs have constructed a variety of arc furnaces, often based on electric arc welding kits contained by silical blocks or flower pots. Though crude, these simple furnaces can melt a wide range of materials, create calcium carbide, etc.

A plasma arc furnace (PAF) uses plasma torches instead of graphite electrodes. Each of these torches consists of a casing provided with a nozzle and an axial tubing for feeding a plasma-forming gas (either nitrogen or argon), and a burnable cylindrical graphite electrode located within the tubing. Such furnaces can be referred to as “PAM” (Plasma Arc Melt) furnaces. They are used extensively in the titanium melt industry and similar specialty metals industries.[10]

Vacuum arc remelting (VAR) is a secondary remelting process for vacuum refining and manufacturing of ingots with improved chemical and mechanical homogeneity.

In critical military and commercial aerospace applications, material engineers commonly specify VIM-VAR steels. VIM means Vacuum Induction Melted and VAR means Vacuum Arc Remelted. VIM-VAR steels become bearings for jet engines, rotor shafts for military helicopters, flap actuators for fighter jets, gears in jet or helicopter transmissions, mounts or fasteners for jet engines, jet tail hooks and other demanding applications.

Most grades of steel are melted once and are then cast or teemed into a solid form prior to extensive forging or rolling to a metallurgically sound form. In contrast, VIM-VAR steels go through two more highly purifying melts under vacuum. After melting in an electric arc furnace and alloying in an argon oxygen decarburization vessel, steels destined for vacuum remelting are cast into ingot molds.

The solidified ingots then head for a vacuum induction melting furnace. This vacuum remelting process rids the steel of inclusions and unwanted gases while optimizing the chemical composition. The VIM operation returns these solid ingots to the molten state in the contaminant-free void of a vacuum.

This tightly controlled melt often requires up to 24 hours. Still enveloped by the vacuum, the hot metal flows from the VIM furnace crucible into giant electrode molds. A typical electrode stands about 15 feet (5 m) tall and will be in various diameters. The electrodes solidify under vacuum.

For VIM-VAR steels, the surface of the cooled electrodes must be ground to remove surface irregularities and impurities before the next vacuum remelt. Then the ground electrode is placed in a VAR furnace. In a VAR furnace the steel gradually melts drop-by-drop in the vacuum-sealed chamber.

Vacuum arc remelting further removes lingering inclusions to provide superior steel cleanliness and further remove gases such as oxygen, nitrogen and hydrogen. Controlling the rate at which these droplets form and solidify ensures a consistency of chemistry and microstructure throughout the entire VIM-VAR ingot.

This in turn makes the steel more resistant to fracture or fatigue. This refinement process is essential to meet the performance characteristics of parts like a helicopter rotor shaft, a flap actuator on a military jet or a bearing in a jet engine.

For some commercial or military applications, steel alloys may go through only one vacuum remelt, namely the VAR. For example, steels for solid rocket cases, landing gears or torsion bars for fighting vehicles typically involve the one vacuum remelt.

Vacuum arc remelting is also used in production of titanium and other metals which are reactive or in which high purity is required.

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Sources

https://en.wikipedia.org/wiki/Electric_arc_furnace

Degner, M. et ali, Steel Institute VDeh (2008), Steel Manual, Düsseldorf Verlag Stahleisen GmbH.

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