Basic Shaped Refractories...

Basic Shaped Refractories  Basic shaped refractories are those refractories which have resistance to corrosive reactions with chemically basic slags, dusts and fumes at elevated temperatures. They are both MgO and CaO based refractories or in combination between them or in combination between MgO and Cr2O3. These refractories belong to MgO- CaO equilibrium system as shown in Fig 1. Fig 1 MgO-CaO equilibrium system  Broadly basic refractories falls into one of the following five compositional categories (Fig 2). Products based on dead burned magnesite (DBM) or magnesia. These products are known as magnesite bricks. Products based on DBM or magnesia in combination with chrome containing materials such as chrome ore. Chrome containing magnesite bricks with about 5 % to 15 % Cr2O3 are known as magnesite chrome bricks while those with 15 % to 30 % chromium are called chrome magnesite bricks. DBM or magnesia in combination with spinel. In these basic bricks magnesia-rich spinel (MgO.Al2O3) replaces chrome ore. These bricks are called magnesite spinel bricks. DBM or magnesia in combination with carbon. These bricks are known as magnesite carbon bricks. Dolomitic products. These bricks are known as sintered dolomite bricks. Fig 2 Categories of basic shaped refractories based on composition  Basic refractories are characterized by an extremely high refractoriness and good resistance to basic slags. Compared to fireclay bricks they do not have glassy phase. These refractories have low resistance both to thermal shocks and creep at temperatures close to 1500 deg C. The chemical-physical characteristics together with a very high thermal capacity and thermal conductivity make basic refractories ideal refractories for steel making processes. Hence basic refractories received increased importance with the introduction of basic oxygen steel making process. One of the more important types of magnesite bricks are those which have low...