## 4 Discussion  
Figure 4 demonstrates a continuous increase in gunning mix consumption throughout the campaign, both in the trunnion area (S9 zone) and in the control slag line area (S3 zone). Figure 5a,b reveals two distinct wear phases in both the trunnion (S9) and slag line (S3) areas during the campaign. These wear phases can be understood through the theoretical framework of progressive refractory degradation. Initially, the MgO-C refractory maintains structural integrity through its carbon phase, which provides resistance to both thermal shock and slag penetration. As this campaign progressed, the first wear phase (1000-7000 heats) likely represents the gradual depletion of the protective carbon phase in localized areas subjected to oxygen jet impingement. The second acceleration phase (11,000-16,000 heats) indicates a transition to advanced degradation where the compromised refractory structure allows more rapid penetration of slag components, creating a self-accelerating wear mechanism. The main focus of this research was to determine if the position of the oxygen lance copper tip towards the inner wall of the BOF had any effect on the wear of the refractory lining in the analyzed areas. This question fundamentally relates to fluid dynamic principles governing oxygen jet impingement and the resulting splash patterns of molten metal and slag. When high-velocity oxygen streams consistently impact specific areas of the lining, they create localized zones where multiple wear mechanisms intensify simultaneously. An accurate analysis of MgO-C lining wear is essential, particularly at heights significantly affected by pure oxygen blowing itself as well as by the splashing and spitting of the liquid metal and slag emulsion. The zone of the lining at a height of 4-5.2 m is the most worn by these wear factors. This height also includes the two opposite areas, known as the trunnion area. To isolate the influence of these mechanisms, the slag line area (5.2-6.2 m) was also monitored as a control zone. From a theoretical perspective, the momentum transfer from the oxygen jets to the molten bath creates predictable splash patterns based on principles of fluid dynamics. The jets create a cavity in the bath surface that oscillates and periodically collapses, ejecting droplets of metal and slag at high velocities along trajectories determined by the jet positioning. This physical model explains why certain areas of the lining receive disproportionate exposure to erosive conditions when jet directions remain fixed. Figure 6a-e details the MgO-C refractory thickness changes in the trunnion and control slag line areas. The control slag line was analyzed to assess the oxygen lance nozzle's directional impact on the trunnion zone. Substantial skull formation occurred mainly in the campaign's first third (up to heat 6000), with renewed skull growth around heat 12,000, coinciding with increased gunning refractory use. Skull deposit formation and dissolution constitute a dynamic equilibrium regulated by thermochemical conditions at the refractory-slag interface, analyzed through phase equilibria and reaction kinetics. Initial skull formation establishes a protective barrier, maintaining steady-state conditions where formation and dissolution rates equilibrate. Progressive slag and refractory compositional changes disrupt this balance, inducing accelerated wear during later campaign stages. The  
renewed skull formation around heat 12,000 likely reflects a critical change in interfacial conditions, with refractory degradation prompting compensatory maintenance. This pattern is consistent with progressive failure models in composite materials, where initial degradation accelerates further damage. The greatest lining loss was recorded between heats 14,739 and 16,400. Subsequently, gunning mixture thickness increased only due to intensive gunning refractory application.