Oxidation – In refractory wear by oxidation, C of the refractory lining is oxidized by reacting either with O2 or FeO in the slag. As the C of the refractory lining reacts, the C content of the refractory decreases and the refractory loses its strength and is washed away. The C oxidation mechanism also occurs at the cold face of the brick if there are holes in the steel shell. O2 from the air reacts with the brick C, and the back part of the brick lining turns into powder.
Erosion – It is another refractory mechanism which is taking place in the EAF. Erosion is the physical wearing of the refractory since the liquid steel and the liquid slag is moving over the face of the refractory lining and physically abrading or eroding the lining. Erosion is a common mechanism for refractory wear at the taphole, slag line, roof electrode openings and the off-take ducts.
Melting – It is one of the wear mechanisms for refractories in the EAF. The unshielded electric arc generates temperatures which are well above the melting point of many refractories. Melting is the simple phase change of the refractory from the solid to the liquid, and the liquid phase when formed is then washed away. Melting can be a serious problem in linings if it is not detected in time and not corrected immediately.
Hydration – Since water is being extensively used in present day EAFs, there are incidences of water leaks. Refractories are easily damaged by water or steam due to the hydration of the MgO or lime contents of the refractory product. Hydration results in expansion of the individual grains comprising the refractory lining. These grains grow and burst, disrupting the lining.
Spalling – Refractory wear due to spalling takes place when the refractory is subjected to rapid heating or rapid cooling. Rapid heating or rapid cooling causes stresses in the lining and when these stresses exceed the inherent strength of the refractory material, then it results into the cracking. When these cracks intersect, chunks of refractory fall out of the lining. This mechanism of refractory damage is frequently observed in the roof refractories since they are exposed to cyclic heating and cooling.
Zones of the EAF
Based on the operating conditions existing in the EAF, the furnace can be divided into specific zones. Each of these zones has the refractory requirements of varying nature. These zones have been shown in Fig 1 and Fig 2. Major zones of EAF are (i) the hearth which contains the liquid steel as well as the initial charge materials, (ii) the slag line which is the transitional area between the hearth and the side wall, (iii) the upper side wall which lies above the slag line, and below the water cooled panels, (iv) the taphole which is the opening provided for tapping of the liquid steel, and (v) the roof which has a refractory portion (occasionally referred to as the delta), (to be followed)处进行编辑.