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Why does the quality of electrode nipple play an important role in EAF steelmaking?

Sep 01, 2020 Source: DanCarbon Writer: Li Feng
Why does the quality of electrode nipple play an important role in EAF steelmaking?
More than 80% of the accidents of using electrodes in EAF steelmaking are caused by the breaking and loosening of the nipples.
The quality of electrode nipple play an important role in EAF steelmaking
Nipples play a key role in the connection of electrodes in steelmaking. The quality of nipples is directly related to the use of electrodes in electric furnace steelmaking. Without high-quality nipples, no matter how great the quality of electrodes is,  problems will arise.
According to the relevant data, more than 80% of the accidents of using electrodes in EAF steelmaking are caused by the breaking and loosening of the nipples. Therefore, the selection of high-quality electrode nipples is the guarantee condition for the normal use of EAF steelmaking electrodes.
Matching of graphite electrode and nipple
In the steelmaking process, the nipple temperature is always greater than the temperature of the electrode at the same horizontal position. As the temperature rises, both the electrode and the joint produce linear expansion. The condition for no gap between the connecting surface of the electrode and the nipple due to expansion is: α nipple <both ends of α electrode.
As long as the linear expansion coefficient of the graphite electrode and the joint are matched properly, there will be no gaps on the connecting surface. At this time, most of the impact force generated by the collapsed material will be borne by the electrode body, and the probability of nipple fracture will be reduced. To prevent expansion and cracking of the nipple hole, it must meet: α nipple radial <α electrode radial.
To meet the above two requirements, it is necessary to ensure that the raw material for the production of the nipple is higher than the raw material for the production of the electrode, especially the thermal expansion coefficient of the former is smaller than the other. In addition, the graphitization temperature of the nipple should be higher than the graphitization temperature of the electrode.
The coefficient of thermal expansion is one of the important physical and chemical indicators of graphite electrodes and nipples. Understand the thermal expansion behavior of graphite electrodes and nipples, and take necessary measures to ensure that electrodes and nipples meet recognized requirements.

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