# Evaluation of Factors Affecting the MgO-C Refractory Lining Degradation in a Basic Oxygen Furnace
## 1 Introduction
However, under operating conditions, mechanical wear factors do not act on the refractory lining alone but in combination with thermal or chemical factors [1; 43]. The use of gunning refractories, slag coating, or slag splashing is an important factor in maintaining the structural integrity of the refractory in BOFs. Repair procedures help protect the MgO-C refractory lining from wear caused by mechanical and corrosive effects while also helping extend the life of the refractories and, therefore, the BOF campaign [3]. Regardless of the treatment method, it is important to note that each lining has a specific critical level of durability beyond which the application of any repair method becomes economically unviable. Gunning refractories are one of the most effective ways to extend the life of an oxygen converter's refractory lining, increasing the number of heats per campaign. The strategic objective of pneumatically applying monolithic refractories to a precisely defined area of the BOF lining is to avoid slowing down the production process due to excessively long breaks for lining repairs, thus, preventing a reduction in steel productivity [1]. Wear evaluation of the BOF refractory is achieved by comparing the MgO-C refractory lining thickness data. The first measurement of the converter's internal profile, made after constructing the new working lining, is taken as the reference. This data shall be considered the benchmark for the entire campaign. Each subsequent measurement shall be compared with the reference measurement to determine the loss (refractory wear) or gain (skulls formation) of refractory in BOFs. During the steelmaking process, a mixture of liquid steel and slag forms deposits on the refractory lining, oxygen nozzle, converter throat, and inner wall of the flue gas duct [44]. These deposits are collectively known as skulls. Determining the chemical composition of the skulls is difficult because the chemical composition of steel and slag changes significantly during the steelmaking process [1]. The aim of treating the refractory lining in the BOF is to reduce the skulls on the structure and maintain the MgO-C lining at an optimum level. The size of the skulls is determined by measuring the lining using laser equipment. A special oxygen nozzle is used in the BOF to remove the skulls. The holes in the copper head can be sealed with copper screws as required to allow the oxygen stream to reach the skull area without hitting the unaffected MgO-C lining [45]. Skills on the oxygen nozzle cause complications when handling the nozzle. It is possible to reduce the formation of skulls on the copper head and the nozzle by introducing a post-combustion sub-lance [1],controlling the molten metal level during the heat process using radar sensors [44], and controlling the height of the oxygen lance during the steelmaking process [45]. Lime and dolomitic lime are the main slag-forming components and are added to form a primary basic slag. The formation of an active high-base slag depends on the flux (CaO and MgO) transfer to the slag. The rate of lime assimilation by the slag is determined by the reactivity of the lime and the dolomitic lime. To delay the formation of high-base slag in the converter and thus excessive wear of the MgO-C lining, soft-burnt lime with high reactivity is used as a slag-forming flux [1,27]. Another factor adversely affecting the MgO-C lining is the high silicon content of the hot metal. A high silicon content in the pig iron prolongs the formation of high base BOF slag, while acidic slag with a high silicon oxide content significantly damages the basic MgO-C lining. Moreover, high silicon in the pig iron decreases the steel yield due to increased metal rejection. In addition, the increased splashing of molten metal and slag causes the formation of skulls on the refractory lining [46]. The volume and intensity of technical oxygen blowing directly influence the wear rate of the MgO-C refractory lining, the level of slag oxidation, and the slag formation process.