발간논문

Home > KJMM 논문 > 발간논문

The pressure at the bottom of the vessel was measured in the N₂and He gas bottom injection into water model system using the pressure transducer to understand the refractory wear at the tuyere mouth. The frequency of bubble formation was measured using the high speed cinematography along with the variation of pressure peaks to check the bubbling jetting transition. The actual pressures of bubbling and jetting were multiplied by each time fraction to obtain the average pressure at the bottom. The average pressure was markedly decreased when the gas velocity was increased over the apparent sonic velocity. The average pressure at the bottom decreased remarkably as the distance from the nozzle increased.

keyword :

As a fundamental study on the physicochemical properties of soda-bearing slags, an equilibrium measurement between hydrogen/water vapour mixtures and the soda-bearing stags of Fe_tO-Na₂O-SiO₂ternary system contained in solid iron crucible at 1400℃ has been made. From the results obtained, the activity of iron oxide and the ratio of Ferric to ferrous in (Fe^(3+)/Fe^(2+)) have been determined as a function of slag composition. The activity of iron oxide in this slag markedly deviated to the direction of N_(Na₂)O/N_(SiO₂)＝⅔. In the view of ionic theory, the approximate validity of regular solution model for cations was examined to evaluate the thermodynamic properties of this ternary slag containing Na₂O. It was confirmed that the regular solution model was satisfied within experimental error except for extremely FeO rich region.

keyword :

The processing conditions of Al-Killed steel strip were investigated for hot dip galvanizing by use of continuous galvanizing line. The Zn-layer adherence to steel and the resistance to crack were increased with increasing coiling temperature after hot rolling. Sol-Al in steel strip was harmful to the Zn-layer adherence, and it is hopeful to control its content below 0.05%. The size of alloy grains seems to be influenced by the Oxide scale on the strip surface after deoxidizing annealing. The higher the hot coiling temperature, the finer the grain size of alloy layer, and the fine grain of the alloy layer seems to strengthen the Zn-layer adherence. But pickling and bend formability being considered, optimum coiling temperature is around 700℃.

keyword :

An injection method using CaCO₃powder and other additives as fluxes was employed for the desulfurization of molten pig iron. The results are as follows: 1. The injection method using CaCO₃powder appeared to have a very effective desulfurization by forming the porous and active fine CaO particles and stirring effect due to CO₂gas formed when CaCO₂gas formed when CaCO₃decomposed 2. Partially substituting of CaCO₃with CaO decreased the desulfurization degree as the content of CaO increase. This means that the ability of desulfurization of CaCO₃is superior to CaO. 3. All addition as reduction agent (deoxidizer) improved the desulfurization degree and this is attributed to the promotion of decomposition reaction of CaO into Ca＋O by lowering the oxygen chemical potential with formation of Al₂O₃. De-si and de-Mn reaction, however, were suppressed by the Al addition.

keyword :

The majority of cracks generated in the continuously cast strands are caused by tensile strains imposed either thermally or mechanically at the solidification front. It is well accepted that the thermal crack is generated as the reheat exceeds about 100℃ on the strand surface. To characterize the surface temperature profile, the cooling part between two supporting rolls of the spray cooling zone was subdivided into four sub-zones and the characteristic heat transfor coefficient in each sub-zone was applied accordingly. By means of computer simulation, effects of parameters, such as spray distance, casting speed, and pouring temperature on the reheating as well as the solidification rate were investigated separately at the spray cooling zone. Results thus obtained were discussed with respect to the cracking susceptibility of the cast strand.

keyword :

With the data of steel and slag compositions obtained by the oxygen sensor, emission spectrometer and fluorescent X-ray, the behavior of oxygen, phosphorus and manganese at LD end-point were studied. For a quantitative determination a multiple regression analysis was made. The results of a statistical investigation comprising about 100 heats indicated the effects of the molten steel compositions, slag compositions and temperature on the behaviors of oxygen, managnese and phorphorus at LD end-point.

keyword :