|Monthly Tech-Tip |
Alternate Names: Dead-burned Dolomite
Dead-burned dolomite is produced when dolomite is calcined at very high temperatures. It is used both as a refractory product in granular form to repair linings and for making the bricks used in the refractory linings of casting ladles and cement kilns.
This refractory work well for ladles because it creates MgO in solution in the slag, which provides an buffering because MgO particles in suspension provide coating protection. Any excess MgO precipitates, protecting refractories and tap holes, reducing the need for gunning and repairs.
An inexpensive source of MgO and CaO for ceramic glazes, also a highly refractory material when fired in the absence of reactant fluxes.
Materials that source Na2O, K2O, Li2O, CaO, MgO and other fluxes but are not feldspars or frits. Remember that materials can be flux sources but also perform many other roles. For example, talc is a flux in high temperature glazes, but a matting agent in low temperatures ones. It can also be a flux, a filler and an expansion increaser in bodies.
Materials that melt at high temperatures. These are normally used for kiln bricks, furniture, etc. or for ceramics that must withstand high temperatures during service.
Calcining is simply firing a ceramic material to create a powder of new physical properties. Often it is done to kill the plasticity or burn away the hydrates, carbonates, sulfates of a clay or refractory material.
|By Tony Hansen|
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