## 3 Results
### Reasons for MgO-C Refractory Wear from a Technological Perspective  
A comprehensive analysis of the total gunning refractory consumption during the campaign revealed that this selected area exhibited significant consumption of gunning in the trunnions area. This is largely influenced by the spitting of metal and slag emulsion. Furthermore, the analysis of gunning refractory material consumption and its location application revealed that the opposite side of the BOF lining (the right trunnion zone; known as the 3 o'clock zone, located in vessel from 75 to 105\({}^{\circ}\) and labeled as S3) had a significantly lower application of gunning refractory mixtures during the whole campaign, thus exhibiting less damage than left trunnion zone labeled as S9 (Figure 7). The substantial difference in the consumption of gunning refractories constituted the basis of the present research. The research focused only on the zone of trunnions, where the imbalance in gunning refractory consumption in opposite regions was a challenge to investigate. Figure 7: A visual representation of the projected oxygen streams blown from a 5-hole BOF lance tip. The MgO–C refractory wear area is shown in red. Based on these significant differences in BOF lining wear and gunning mixture consumption during the campaign, it can be concluded that the orientation of the oxygen lance tip nozzles has a significant effect on the location of wear and is the determining factor that defines the location of excessive wear in the trununion area (Figure 7). During the whole campaign, when the worn oxygen lance tip was replaced, the orientation of the nozzles relative to the MgO-C lining never changed and the new 5-hole tip still had the same orientation relative to the lining as the worn one. Gunning mixtures were also applied to the control slag line zone during the campaign under review, but their use was related to the well-known effect of BOF slag within this zone. In addition, the slag line zone was also mechanically damaged (abrasion) as the loaded fluxes impacted the slag line zone during each heat when the fluxes were loaded via chute. This caused build-up (skulls) on the MgO-C lining in the slag line zone (S3 zone), which had to be removed using a special oxygen deskulling lance, putting excessive stress on the basic refractory lining in the mentioned zone, which in turn required increased consumption of repair gunning refractory mixtures. Two basic methods were employed during the campaign to repair the MgO-C refractory lining: gunning of refractory mixtures and slag coating technology. The slag coating technology was used up to 6 times per day throughout the 946-day campaign, depending on the condition of the refractory lining. This method was selected due to its high efficiency and low cost. A further high magnesium oxide flux was added to the residual BOF slag from the previous heat, and by tilting the vessel to either side, this high-base slag formed a protective coating on the refractory walls. It is evident that the modified high-basic slag can be applied to the MgO-C lining in the area of the charge pad, tap pad, part of the slag line, and the bottom of the BOF lining. However, the side walls of the BOF lining, i.e., the trununion area and the specific side area of the slag line, cannot be treated by the slag coating technique (Figure 8a). Wherever the slag coating technology could not be applied, or where the MgO-C lining in the BOF was not sufficiently protected by slag coating, the gunning of the refractory mixtures is used. By using gunning technology, it was possible to apply the gunning mixture to any location of the MgO-C lining in the BOF. The necessity for the use of gunning was evaluated based on the inspection of the condition of the BOF lining after each heat and the results from the laser measurement of the MgO-C lining.