## 4 Discussion
This position management ensures uniform wear of the MgO-C refractory lining in the trunnion area (S3 zone and S9 zone) of the BOF. Figure 10: The principle of rotation of the copper tip of the oxygen lance during its replacement from the initial position (Period 1) to the turned position (Period 2): (**a**) 4-hole tip; (**b**) 6-hole tip. Figure 9: The diagram illustrates a proposed method for reducing the localized wear of the BOF refractory lining in the case of 5-hole tip deployment. Turning the copper tip from the initial position (Period 1) to the turned position (Period 2). For a 4-hole copper tip (Figure 10a), the rotation strategy creates distinct exposure cycles that have theoretical advantages for refractory maintenance. In the initial position of the tip (Period 1), both opposite trunnion areas are subjected to wear at the same time; after turning the copper tip (Period 2), none of the oxygen jets will interfere with the area of the trunnions (neither S3 zone, nor S9 zone). This means that during Period 2 of such an oriented copper tip, there will be no excessive consumption of gunning mixtures in the trunnion area because the trunnion area (neither S3 zone, nor S9 zone) will not be excessively stressed by the oxygen jet or by direct splashing and spitting of molten steel and slag. Combined with the slag coating technique or slag splashing technology used, the consumption of repair gunning refractory mixtures will be all the lower. During the next rotation by 45\({}^{\circ}\) (Period 1) of the 4-hole copper tip, both the oxygen jet and the molten emulsion of metal and slag will affect both areas of the trunnion, which will also need to be treated with gunning mixtures. However, the saved gunning mixtures from the previous rotation period means a direct saving in the cost of repairing the BOF lining during the campaign. By maintaining regular rotation of the copper tip of the oxygen lance, sustained saving of gunning mixtures can be achieved in the highly exposed area of the trunnions, and this can be achieved throughout the BOF campaign. If slag splashing technology is used in addition to the proposed 4-hole tip rotation management, the effect of saving money spent on repairing the MgO-C refractory lining in the BOF will be even more pronounced. This cyclic exposure pattern interrupts the progressive degradation mechanism that typically accelerates wear in fixed impact zones. The alternation between exposure and protection creates a wear management strategy that aligns with theoretical models of material recovery under cyclic stress conditions. During protected periods, maintenance techniques such as slag coating can achieve maximum effectiveness, allowing partial healing of the thermal damage and creation of protective layers before the next exposure cycle begins. Similarly, with a 6-hole copper tip rotated by 30\({}^{\circ}\) during replacement (Figure 10b), the trunnion areas experience alternating periods of exposure and protection. After the copper tip is turned by 30\({}^{\circ}\) during replacement (Period 2), none of the jet will directly hit the MgO-C refractory lining in the area of the trunnions (neither the S3 zone nor the S9 zone). The benefits of managing the rotation of the oxygen lance copper tip are significantly enhanced when combined with slag splashing technology. With slag splashing, it is also possible to cover the exposed zones S3 and S9 with slag, which cannot be treated with slag coating technology. The combination of copper tip rotation of the oxygen lance and slag splashing technology further reduces the amount of gunning mix required, improving cost-effectiveness. Although there is no direct hit to the trunnion area during Period 2 (for 4-hole, 5-hole, and 6-hole tips), there is wear to new areas that are not fully reached by the slag coating technology and thus need to be repaired by the gunning of refractory mixtures (if the slag splashing technique in not available).