The Influence Of The Microstructure Of The Lime To The Hot Metal Desulphurization Pretreatment

Sulfur is harmful to the hot workability of steel. It can generate hot brittleness. So it isthe harmful element in the most of steel grade. The key to smelting low sulfur steel withhigh added value is to control the content of sulfur. There are strict requirements for thecontent of sulfur in the most of steel grade. The sulfur in hot metal is well removed in thehot metal pretreatment and the cost is low. Lime is a kind of desulfurizer in the hot metalpretreatment. The desulfurization performance is affected by its microstructure. All sorts ofchange rules of different microstructure lime in the process of hot metal pretreatment wereresearched. In order to improve the rate of the desulphurization, the influence rule of limemicrostructure was discussed in the desulfurization process of hot metal pretreatmentThrough different conditions and different devices the lime of different structurewas calcaned and the activity degree was measured. The desulfuration residue wasprepared with the lime of different microstructures. The desulfurization experiments ofhigh sulphur molten iron with the desulfuration residue were studied. The surfacestructure of the lime and desulfuration residue was shot by SEM. The presence anddistribution of sulfur in slag was analyzed by experiment measures such as XRD. Thetotal pore area, average pore diameter and total pore volume of lime were measured bymercury porosimeter. The sulfur content in steel samples was measured by chemicalmethods and desulfurization rate was calculated. The relationship between spacestructure, grain size, total pore area, calcinations conditions, active degree anddesulfurization rate was created. The results showed that: at the low temperature with theincrease of time the active degree and the desulfurization rate was increased. At the hightemperature with the increase of time the active degree and the desulfurization rate wasincreased at the start and then reduced. When the constant time was short, with theincrease of calcination temperature the active degree and the desulfurization rate wereincreased. When the time was long, with the increase of temperature the active degreeand the desulfurization rate was increased at the start and then reduced. The average porediameter, the total pore area and grain size is not the bigger the better. It was the interplayamong them and there was an optimal value.