In the Usinor Sacilor device, the DCEAF anode is made of a steel rod that goes through the furnace bottom. A water cooled jacket is set at the electrode base and limits the melting of the rod. At LME steelplant, the electrodes are surrounded by refractory sleeves of precooked phosphate bonded magnesia-spinel concrete, embedded in magnesia and magnesia-dolomite ramming mixes. Refractory plays a key role as the geometry of the molten electrode relies on the refractory stability. Their wearing limits the electrode and furnace bottom life. This study presents the damage mechanisms that affect the top and the base of the refractory device at LME and the critical points of their design. The electrode shortens and its top widens as a consequence of the thermomechanical fracturing of the upper sleeve. When the furnace is restarted after every weekend, a thermal shock affects the upper sleeve face that quickly dilates in contact with the molten steel. It creates strong vertical tensile stresses that exceeds the strength of the brittle cold concrete. These dangerous stresses can be avoided by setting a thermal insulation on the upper sleeve prior to every furnace start-up. These short-life elements favour a radial heating of the sleeve by the electrode. High hoop stresses still develop but the vertical breaking of the sleeve induces only little wearing. At LME steelplant, the upper sleeve is now protected under a ramming layer or a cheap concrete ring at every re-start. This practice decreased the rate of vertical shortening of the electrode by half. Campaign is now limited by the refractory damage where the electrode goes through the furnace shell. Risks of short-circuit increase then with the probability of metal infiltration from the electrode to the shell. In LME furnace, electrode is extended under the shell in a <<shaft>> surrounded by a steel flange. The thermal expansion of the lower sleeve is restrained at this level after the ramming has sintered around. Corrosion of the concrete is enhanced after open fractures channel the liquid oxides contained in the molten electrode. More precisely sintering of the ramming involves the electrode oxides that migrate in the refractory porosity, dissolve the concrete phosphate binder and re-precipitate solid phases further at lower temperature. Liquid impregnated concrete becomes plastic near the inner hot face and gets a permanent strain in the shaft. Everytime the furnace stops, permanent tensile stresses rise on cooling in the lower sleeve and produce the described open fractures. In order to improve the refractory behaviour, it is necessary to limit the thermal expansion restraint of the lower sleeve. The surrounding ramming should remain soft, easy to deform by grain to grain sliding. A thicker ring of ramming is also required in a shaft with a maximum diameter to height ratio. An even better furnace conception is to keep the electrode melting line higher, several decimeters from the shell. It can be achieved with a thicker furnace bottom and a more efficient cooling system. This was experienced in more recent furnaces. With these modifications, it is now possible to get a life of the electrode longer than 2000 heats.
