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Anti-oxidation Coating And Graphitization Furnace

Release time:2019-11-04 From: Zhengnai Industry in China

Advantages of graphite electrodes with anti-oxidation coating

As a result of actual use, the graphite electrode with anti-oxidation coating can reduce the net consumption of electrode per ton of electric furnace steel by 20%~30% compared with graphite electrode of the same quality but without anti-oxidation coating, and can reduce the steel per ton of steel. The power consumption is about 5%, and the cost of adding an anti-oxidation coating is about 10% of the sales price of the graphite electrode.
 

Anti-oxidation coating in graphite electrode

Anti-oxidation coating performance can meet 3 requirements
The resistivity of 0.07 to 0.1 μΩ·m .
Gas impermeability lasts for more than 50h at 900℃.
Coating decomposition temperature is above 1850℃.


 

Impregnation method for producing antioxidant coating

Another anti-oxidation coating is produced by some salt solution impregnation method, such as impregnation of the graphite electrode with a solution such as phosphate or borate, and then heat treatment at a suitable temperature to evaporate the water so that the surface of the electrode is immersed. The impregnating agent in the pore forms an anti-oxidation furnace-preserving film, which acts to suppress oxidation. The oxidation temperature is also greatly different depending on the type of impregnating material used and the impregnation process. This solution impregnation method also increases the mechanical strength of the electrode, but also increases the modulus of elasticity. Therefore, the anti-oxidation effect of the graphite electrode impregnated with the salt solution at high temperatures is not satisfactory.
 

The process points of “alternating spraying-sintering method

The main point of this process is to first process some shallow trenches on the outer surface of the graphite electrode, then place the electrode in a heating furnace to heat to about 250 ° C, then spray a thin layer of aluminum on the surface of the electrode with a metal spray gun, and then in aluminum A layer of refractory mud is sprayed on the outside of the layer. Finally, the high temperature generated by the arc is used to fuse the aluminum and the refractory mud together to form a cermet layer which is both electrically conductive and resistant to high temperature oxidation. In order to achieve a certain thickness of the coating, aluminum spraying and spraying The refractory mud and the subsequent arc burning are repeated 2 or 3 times.
 

In the steelmaking furnace using an oxidation resistant coating

The electric furnace steel plant uses the anti-oxidation coating electrode to modify the electrode holder of the steelmaking furnace, appropriately enlarge the inner diameter of the handle, and then insert a plurality of graphite pads into the curved shape on the inner side to make the anti-oxidation coating The graphite electrode introduces a current through the graphite pad. If the anti-oxidation coating is directly in contact with the gripper, the spark is easily generated on the non-smooth contact surface to damage the gripper.


 

Acheson graphitization furnace

The structure of the Acheson graphitized furnace is relatively simple. It is transformed on the basis of the electric resistance furnace for producing silicon carbide. The main feature is that the calcined product and the electric resistance material which are put into the furnace together form a furnace resistance, and the high temperature is generated to make the roasting graphitization.
The Acheson Graphite Furnace has a long history and has been in the carbon plant for over 100 years.
 

“U” type graphitization furnace

It is a kind of Acheson graphitization furnace, which has the advantages of improving the thermal efficiency of the graphitization furnace and saving electric energy, but there is a disadvantage that the current distribution in the furnace is not uniform, so the quality of the graphite electrodes installed in different parts is different, and The middle partition wall is easy to burn out.

Index of UHP/RP Graphite electrode

Item Unit UHP RP
300-600mm 650-800mm 300-800mm
Electric resistivity Electrode μΩm 4.8-5.8 4.6-5.8 7.8-8.8
Nipple 3.8-4.5 3.8-4.5 5.0-6.5
Flexural strength Electrode Mpa 10.0-14.0 10.0-14.0 7.0-12.0
Nipple 20.0-26.0 22.0-26.0 15.0-20.0
Elastic modulus Electrode Gpa 9.0-13.0 10.0-14.0 7.1-9.3
Nipple 15.0-18.0 15.0-18.0 12.0-14.0
Bulk density Electrode ≥g/cm3 1.68-1.74 1.70-1.74 1.53-1.56
Nipple 1.77-1.82 1.78-1.84 1.70-1.74
CTE(100-600℃) Electrode x10-6/℃ 1.1-1.4 1.1-1.4 2.2-2.6
Nipple 0.9-1.2 0.9-1.2 2.0-2.5
Ash   0.3 0.3 0.5

 

Mobile graphitization furnace

The mobile graphitization furnace is built on a rail car with a steel structure. The rail car can be moved to the left and right along the track laid on the ground. The loading and unloading products and the power supply can be set in two workshops respectively, which will connect the transmission of the graphitization furnace. The length of the busbar is greatly shortened.
 

Internal heat tandem graphitization furnace

This is a production process in which the calcined product is graphitized by using an electrode column which is directly connected in series by a plurality of calcined articles without using an electric resistance material. Because it fully utilizes the self-resistance heat of the baked semi-finished product and the faster heating rate, it consumes 20%~35% less than the Acheson graphitization furnace.
 

 

Indirect heating continuous production graphitization furnace

The horizontal two-channel continuous production graphitization furnace for the production of small electric carbon products has a fixed high temperature zone, and the high temperature zone is made of graphite sheet. This continuous production graphitization furnace adopts two-way countercurrent feed and does not need to be protected by inert gas.
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