Graphite electrodes, mainly made of petroleum coke and needle coke as raw materials and coal pitch as binding agent, are made by calcining, batching, kneading, pressing, roasting, graphitization, and machining, and are released in arc furnaces as arcs. The conductor that heats and melts the charge by electrical energy can be classified into normal power, high power, and ultra-high power, depending on the quality index.

classification

Graphite electrodes include:

(1) Ordinary power graphite electrode

It is allowed to use graphite electrodes with a current density of less than 17 A/cm2, which is mainly used for ordinary power furnaces such as steelmaking, silicon refining, and smelting of yellow phosphorus.

(2) Anti-oxidation coating graphite electrode

A graphite electrode coated with an anti-oxidation protective layer (graphite electrode anti-oxidant). Form a protective layer that is both conductive and resistant to high temperature oxidation, reduces electrode consumption during steelmaking (19% to 50%), extends electrode life (22% to 60%), and reduces electrode energy consumption. The use of this technology can bring about such economic and social effects:

1 Graphite electrode unit consumes less, production costs have a certain reduction. For example, in a steel plant, there were no production shutdowns of 35 graphite electrodes per week for the first class LF smelters, and consumption of 165 furnaces for the refining process was calculated at the end of the year. After the graphite electrode anti-oxidation technology was used, 373 units (153 tons) per year were saved. ) Electrode, calculated per ton of ultra-high power electrode 16,900 yuan per year, can save 2,558,700 yuan***.

2 The graphite electrode consumes less power, saving the unit's electricity consumption, saving production costs and saving energy!

3 As the number of graphite electrode exchanges is smaller, the amount of labor and risk factors of the operating workers are less, and the production efficiency is improved.

4 Graphite electrodes are high-consumption and high-pollution products. Today, the promotion of energy-saving and emission-reducing environmental protection has very important social significance.

This kind of technology is still in the stage of research and development in China, and some domestic manufacturers also started production. In Japan and other developed countries have been more widely used. At present, there are also companies that have imported special anti-oxidation protective coatings in China.

(3) High-power graphite electrodes. It is allowed to use a graphite electrode with a current density of 18-25 A/cm2, which is mainly used for steel-making high-power arc furnaces.

(4) Ultra-high-power graphite electrodes. It is permissible to use graphite electrodes with current densities greater than 25 A/cm2. Mainly used for ultra high power steelmaking electric arc furnaces.

Graphite electrode advantages

Note: graphite electrode for EDM, also known as copper

1: The increasing complexity of mold geometry and the diversification of product applications have led to higher and higher requirements for the accuracy of spark discharge. The advantage of the graphite electrode is that it is easy to process, the removal rate of the discharge machining is high, and the loss of the graphite is small. Therefore, some of the group-based spark machine customers give up the copper electrode and change to the graphite electrode. In addition, some special-shaped electrodes cannot be made of copper, but graphite is easier to form, and the copper electrodes are heavier and are not suitable for processing large electrodes. These factors have caused partial group-base spark machine customers to use graphite electrodes.

2: Graphite electrodes are easier to process and the processing speed is significantly faster than that of copper electrodes. For example, the use of milling processing of graphite, the processing speed is 2 to 3 times faster than other metal processing and does not require additional manual processing, while the copper electrode requires manual manipulation. Similarly, if electrodes are manufactured using high-speed graphite processing, the speed will be faster and the efficiency will be higher, and no dust problem will occur. In these processes, choosing the right tool and graphite hardness can reduce the wear of the tool and the damage of copper. If specifically comparing the milling time of the graphite electrode and the graphite electrode of the copper electrode, the graphite is 67% faster than the copper electrode. In the general case of discharge processing, the graphite electrode processing is 58% faster than the copper electrode. As a result, the processing time is greatly reduced, while also reducing manufacturing costs.

3: The graphite electrode is different from the traditional copper electrode design. Many mold factories usually have different allowances for rough machining and finishing of copper electrodes, while graphite electrodes use almost the same amount of reservation, which reduces the number of CAD/CAM and machine processing. For this reason alone, Sufficient to improve the accuracy of the mold cavity to a large extent.

Of course, after the mold factory switches from a copper electrode to a graphite electrode, it should be clear first how to use the graphite material and consider other related factors. Today, some group-based spark machine customers use graphite for electrode discharge machining, which eliminates mold cavity polishing and chemical polishing but still achieves the desired surface finish. Without increasing the time and polishing process, copper electrodes cannot make such workpieces. In addition, graphite is divided into different grades. The use of appropriate grades of graphite and spark discharge parameters under specific applications can achieve ideal processing results. If the operator uses the same parameters as the copper electrode on the spark machine using the graphite electrode, The result is certainly disappointing. If it is necessary to strictly control the material of the electrode, the graphite electrode can be set to a non-depletion state (loss is less than 1%) during rough machining, but the copper electrode is not used.

Graphite has the following excellent properties unmatched by copper:

Processing speed: high-speed milling rough machining 3 times faster than copper; high-speed milling precision machining 5 times faster than copper

Good machinability enables complex geometry modeling

Light weight, less than 1/4 of the density of copper, the electrode is easy to hold

The number of individual electrodes can be reduced because it can be bundled into a combination electrode

Good thermal stability, no deformation, no processing burr.