No abstract

At the Egyptian Iron and Steel Company, attention is constantly focused on improving basic steel making practice with the aim of improvement of blowing regime and the addition of forming slag materials system. A number of factors considered important in controlling the properties of steel products and affecting the residual manganese in the basic Oxygen furnace (BOF) have been investigated by changing some industrial parameters, aiming at optimizing the residual manganese in BOF. The studied factors were manganese oxide in the slag, iron oxide in the slag, tapping temperature, Slag basicity, Lance height, blowing time, and carbon content. It was found that residual manganese increased from 0.25 to 0.35 % wt, due to the reduction of both MnO in slag from 22% to 15% and FeO from 21 to18%, also the increase of tapping temperature from 1650 oC to 1670 oC caused an increase the residual manganese from 0.27% to 0.35%, and the slag basicity decrease from 4.25 to 3.8 led to an increase in the residual manganese from 0.25 to 0.37%. Also, the change of the lance height from 1050 mm to 825 mm caused an increase in the residual manganese from 0.27 % to 0.33 %. These results are believed to be reflected on the total energy consumption and ferromanganese additions needed for producing specific grades.

Iron-base superalloys are well known materials having excellent high temperature properties .They are used in turbo superchargers and turbine engines required for aerospace and power plants. In this investigation precipitation hardenable X5NiCrTi26-15 was used to study the influence of microstructural changes on the creep behavior at different conditions . Different creep cycles were applied for both base alloy and laser beam welded alloy (6kW CO2 ) namely at 600 , 625 and 650C at applied controlled creep stresses of 400 and 450 MPa . The base material sheet was used in as solution annealed state ( 30 min, 960 C, WQ ).The specimens were hardened in two steps (24h,760 C, FC and 16 h, 705 C,AC ) before being investigated . The microstructural changes due to grain boundary sliding, intergranual fracture perpendicular to the metal flow axis , and the type ,morphology of different secondary carbides were measured and discussed . To examine the changes in microstructure Philips EM 400 TEM with an acceleration voltage of 120KV, and SEM as well as light microscopy were used . It was found that , laser beam welded structure investigated after creep deformation at temperatures lower than 650C and at controlled stress of 400 and 450 MPa , showed a textured weld metal zone with dendrite having lower hardness combined with a higher creep resistance than that for base material .It was found also that creeping at 650C at the same stress values offsets any gain in creep resistance of welded joints as compared with that for the base material at the same conditions.