Of Mgo Containing Sialon-based Casting Material Rheology, Sintering Properties And High Temperature Performance

In this work, the influences of ultra fine powders, alumina and bauxite-based ?-Sialon fines on the rheological behaviour and high temperature properties of magnesia-based castables have been studied. The purpose of this work is to find the optimum composition ratio of the castable and appropriate content of Sialon addition.The work can be divided into four parts: (1) The influences of ultra fine powders, dispersants and Sialon fines etc. on rheological behaviour of the castable matrix have been studied by using viscometer of model NXS-11A. (2) The influences of ultra fine powders, dispersants, and Sialon fines etc. on castable rheological behaviour have been studied by using flowing table and IBB Rheometer Vl.O. (3) The influences of ultra fine powders, alumina fines and Sialon fines on the properties at room temperature (such as porosity, bulk density, MOR and CCS etc.) of castables after drying at 110? X 24h and firing at 1100? X 3h and 1600? X3h have been studied. (4) The influences of ultra fine powders, alumina fines and Sialon fines on high temperature properties (such as HMOR, TSR and Oxidation resistance) of castables have been studied.The results show that:1) The rheological behavior of the matrix belongs to Bingham model. Ultra fine powders and dispersants are the principal factors influencing the theology of matrix. Microsilica can improve the matrix rheology more remarkably than ultra fine alumina and the content of microsilica is from 0 to 3%. The dispersant trimeric sodium phosphate can work best among the system and its addition is 0.35% or so.Sialon fines have slightly negative effect on the matrix rheology, which can be offset by using the effective dispersant.2) Ultra fine powders, disperants, the ratio of 200mesh/325mess magnisa fines, alumina fines and Sialon fines can influence the rheological behaviour of the MgO-based castables. Ultra fine alumina has little negative effect on the rheological behaviour of the castable and the content addition is 0-4%. Increasing the ratio of microsilica among the micropowders can improve the rheology of the castable to some degree and the better rheological behavior of the castable can be gained when the ratio of ultra fine alumina to microsilica is about 50:50. Sodium tripolyphosphate can work best with about 0.35% additon.The rheological behavior of the castable can be unproved when the ratio of fine magnesia of 200 mesh to 325 mesh is below 1:2. The addition of fine alumina can contribute to the rheological behavior of the castable with no more than 15% addition.Sialon fines have slightly negative effect on the rheological behaviour of the castable. As to the system studied, the content of Sialon is from 0 to 7.5%.The rheology of the castables can be gently decreased with Sialon addition from 0-7.5%, which has little effect on the applying of the castable.3) Ultra fine alumina can improve the properties of sintering with less than 4% addition. The micro silica is better than ultra fine alumina for the improvement of the properties of sintering, but the ratio of micro silica to ultra fine alumina should not be more than 50/50.It has slightly effect on the properties of sintering when the ratio of the aggregate to the matrix is between 70/30 and 60/40. With the fine magnesia 325 mesh increase, the MOR and CCS increase after heat-treating. The linear changes of the specimens become gently expansive, and the MOR and CCS are gently increased with alumina fines increase from 0 to 15%.The bulk density of the specimens decreases and the porosity increases with the Sialon addition the MOR and CCS of the specimens are increased with Sialon addition after fired in!600? for3h.4) With the increase of alumina fines( 0-15%), the TSR of the specimens is increased (45%-72%).The TSR of the specimens increases (63%-95%) with Sialon addition (0-10%), indicating that Sialon additon can improve the TSR.5) The MOR-T curves of this system belong to the type I.The appropriate ratio of ultra fine alumina to micro silica is 75/25 - 50/50 or so, whic...