Zhou Hua Carbon

Graphite electrode manufacturer and other graphite products export

[graphitepro-blog]

Graphite electrodes should be used strictly according to instructions

Graphite electrodes are not unfamiliar to each of us. The main component is graphite, which has become the best conductive material today. Graphite electrodes also need to strictly follow the instructions during use.

Firstly, open the protective cap on the hole to check the integrity of the electrode thread.

Under the premise of determining the integrity, the next step is to clean the internal thread of the hole and the surface of the spare graphite electrode.

Insert the connector into the electrode hole, and the electrode hanger is connected to the other end.

Remove the electrode. Take care not to let the electrode collide with other fixtures.

Hang the spare electrode above the electrode to be connected. When the two electrode end faces are 10-20mm apart, clean the exposed ends of the two electrode ends and the joints again with compressed air, and be lighter to avoid damage to the electrode holes and the threads of the joints.

Tighten the spare electrode.

We need to remind everyone here that if the graphite electrode is found to be wet, it should be dried. More use considerations from china-graphiteelectrode.com

1. Dry graphite electrodes before use.

2. Remove the protective foam cap from the spare graphite electrode hole, and check whether the internal thread of the electrode hole is complete.

3. Use compressed air that does not contain oil and water to clean the surface of the spare graphite electrode and the internal thread of the hole; avoid cleaning with steel wire clumps or metal brushes.

4. Carefully screw the connector into the electrode hole of one end of the spare graphite electrode (it is not recommended to directly insert the connector into the electrode removed from the furnace). Do not hit the threads.

5. Screw the electrode spreader (graphite spreader is recommended) into the electrode hole on the other end of the spare electrode.

6. When lifting the electrode, place a loose object under the end of the spare electrode mounting joint to prevent the ground from damaging the joint; use a hook to reach into the lifting ring of the spreader and lift it, and lift the electrode smoothly to prevent the electrode from loosening from the B end Disengage or collide with other fixtures.

7. Hang the spare electrode above the electrode to be connected, and slowly drop it after aligning the electrode hole; rotate the spare electrode so that the spiral hook and the electrode rotate together and fall; when the end faces of the two electrodes are separated by 10-20mm, use compressed air again Clean the two end surfaces of the electrode and the exposed part of the connector; when the electrode is fully lowered at the end, it should not be too strong, otherwise the electrode hole and the thread of the connector will be damaged due to violent collision.

8. Use a torque wrench to screw the spare electrode until the end faces of the two electrodes are in close contact (the correct connection gap between the electrode and the connector is less than 0.05mm).

[graphitepro-blog]

The realization of the graphitization process

The graphitization of carbon material is carried out at a high temperature of 2300-3000 °C, so it can only be realized by electric heating in the industry, that is, the current directly passes through the heated calcined product, and the calcined product charged into the furnace is generated by the electric current at a high temperature. The conductor is again an object that is heated to a high temperature.

Furnaces currently widely used include Acheson graphitization furnaces and internal heat cascade (LWG) furnaces. The former has a large output, a large temperature difference, and a high power consumption. The latter has a short heating time, low power consumption, uniform electrical resistivity, and is not suitable for fitting.

The control of the graphitization process is controlled by measuring the electric power curve that is suitable for the temperature rise condition. The power supply time is 50-80 hours for the Acheson furnace and 9-15 hours for the LWG furnace.

The power consumption of graphitization is very large, generally 3200-4800KWh, and the process cost accounts for about 20-35% of the total production cost.

Inspection of graphitized products: appearance tapping, resistivity test

Machining: The purpose of mechanical machining of carbon graphite materials is to achieve the required size, shape, precision, etc. by cutting to make the electrode body and joints in accordance with the requirements of use.

Graphite electrode processing is divided into two independent processing processes: electrode body and joint.

The body processing includes three steps of boring and rough flat end face, outer circle and flat end face and milling thread. The processing of conical joint can be divided into 6 processes: cutting, flat end face, car cone face, milling thread, drilling bolt And slotting.

Connection of electrode joints: conical joint connection (three buckles and one buckle), cylindrical joint connection, bump connection (male and female connection)

Control of machining accuracy: thread taper deviation, thread pitch, joint (hole) large diameter deviation, joint hole coaxiality, joint hole verticality, electrode end face flatness, joint four-point deviation. Check with special ring gauges and plate gauges.

Inspection of finished electrodes: accuracy, weight, length, diameter, bulk density, resistivity, pre-assembly tolerance, etc.

[graphitepro-blog]

Graphite beneficiation processing method

1. Beneficiation processing method of crystalline graphite

Crystalline graphite has good natural floatability. In China, flotation is mainly used for beneficiation. Since the size of the graphite scale is one of its most important quality indicators, a multi-stage grinding and multiple-selection process is used in the selection method to select large scale graphite as early as possible. The commonly used collectors for flotation are kerosene, diesel oil, etc., the foaming agent is No. 2 oil, No. 4 oil, etc., the adjusting agent is lime, sodium carbonate, and the inhibitor is water glass.

2. cryptocrystalline graphite beneficiation processing method

The cryptocrystalline graphite crystal is extremely small, so it is also called microcrystalline graphite. Graphite particles are often embedded in clay, and separation is difficult. Due to the high grade of ore (generally containing 60% to 80% of carbon), many graphite mines directly produce crushed ore and sell graphite powder products. At present, some units like zhouhua carbon are still conducting research on new microcrystalline graphite flotation processes (such as oil agglomeration flotation).

3. Purification processing of graphite products

The requirements of modern industry for graphite products are developing in two aspects: one is to require high crystal size to achieve high purity, and the other is to require ultrafine particles (such as less than 1 μm or 0.5 μm). China has established graphite purification and fine powder processing lines in graphite processing plants  The purification method is mainly chemical purification. The most mature process for chemical purification of graphite is to use a caustic alkali and graphite to melt at 700 ° C, then wash to neutral, then add hydrochloric acid to treat and wash, so that the carbon content of graphite reaches 98% to 99%. Some manufacturers also use hydrofluoric acid to produce high-purity graphite.

[graphitepro-blog]

Factors affecting the graphitization of cast iron

The structure of cast iron depends on the extent to which graphitization is carried out. In order to obtain the desired structure, the key is to control the extent to which graphitization proceeds. Practice has proved that the chemical composition of cast iron, the cooling rate of cast iron crystallization and the overheating and standing of molten iron affect the microstructure of graphitization and cast iron.

1. The influence of chemical composition

Among C, Si, Mn, P, and S which are common in bismuth iron, C and Si are elements which strongly promote graphitization, and S is an element which strongly inhibits graphitization. In fact, the influence of each element on the graphitization ability of cast iron is extremely complicated. The influence is related to the content of each element and whether it interacts with other elements, such as Ti, Zr, B, Ce, Mg, etc., which hinder graphitization, but if its content is extremely low (such as B, Ce<0.01%, T< At 0.08%), they also showed a role in promoting graphitization.

2. The effect of cooling rate

In general, the casting cooling rate tends to be slow, and the more favorable it is to perform crystallization and transformation according to the Fe-G stable state diagram, and to fully perform graphitization; otherwise, it is advantageous to perform crystallization and transformation according to the Fe-Fe3C metastable state diagram. Finally, white iron was obtained. In particular, in the graphitization at the eutectoid stage, since the temperature is low, the cooling rate is increased, and atomic diffusion is difficult, it is usually difficult to sufficiently carry out graphitization in the eutectoid stage.

The cooling rate of cast iron is a comprehensive factor related to the casting temperature, the thermal conductivity of the molding material, and the wall thickness of the casting. And usually these factors have the same effect on the two phases.

Increasing the casting temperature retards the cooling rate of the casting, which promotes both the first stage of graphitization and the second stage of graphitization. Therefore, increasing the pouring temperature can pulverize graphite to a certain extent, and can also increase the eutectoid transformation.

3. The effect of overheating and high temperature standing on cast iron

In a certain temperature range, increasing the superheat temperature of molten iron and prolonging the time of high temperature standing will lead to the refinement of the graphite base in the cast iron and increase the strength of the cast iron. Further increasing the degree of superheat, the nucleation ability of the cast iron is reduced, so that the shape of the graphite is deteriorated, and even the free cementite is present, so that the strength is rather decreased, and thus there is a 'critical temperature'. The critical temperature depends mainly on the chemical composition of the molten iron and the cooling rate of the casting. It is generally believed that the critical temperature of ordinary gray cast iron is about 1500-1550 °C, so it is always desirable to have a higher iron temperature.

[graphitepro-blog]

How to avoid the phenomenon that graphite electrode is broken during smelting

Many manufacturers report that electrode breakage often occurs in smelting, which not only increases production cost, increases production cycle, but also is very troublesome to salvage waste graphite electrode. The following measures can be taken to effectively avoid graphite electrode breakage during steel making. And tripping situation:

1) The phase sequence of the graphite electrode is correct, which is counterclockwise.

2) The steel scrap is evenly distributed in the steel furnace, and the large scrap steel material is placed at the bottom of the furnace as much as possible.

3) Avoid the presence of non-conductive materials in the scrap.

4) The electrode column is centered with the top hole of the furnace, and the electrode columns are parallel. The wall of the furnace top hole should be cleaned frequently to avoid the accumulation of residual steel slag and break the graphite electrode.

5) Keep the state of the electric furnace tilting system in good condition so that the electric furnace tilts to maintain balance.

6) The electrode holder is protected from being caught at the electrode connection and the electrode joint hole.

7) Select a joint with high strength and high precision.

8) The torque applied when the electrodes are connected should be appropriate.

9) Prevent the mechanical damage of the electrode hole thread and the joint thread before and during the connection of the graphite electrode.

10) Prevent the connection of steel slag or foreign matter on the electrode holes and joints.