Fundamental Design of Steelmaking Refractories

3 Packing, Stress, and Defects in Compaction

3.1 Introduction

Shaping can be defined as the processing step in which a system constituted by isolated particles is transformed into a consolidated body with a specific shape, size, and microstructure. The selection of one or another industrial-scale shaping procedures is based on the required characteristics of the sintered form—shape and size of the material, microstructure—grain size and shape, dispersion of secondary phases, and density—on the number of pieces to be produced and its necessary reliability, and on environmental and economic aspects. The most expensive stage of fabricating pieces of hard materials such as submerged entry nozzle (SEN) is final machining; thus, great effort is devoted to developing shaping procedures to avoid machining.

Fabrication of shaped refractory by dry pressing a wide range of particles (for example, 6 mm to less than 1 μm) is a preferred and most widely used forming protocol to manufacture ceramic components. Lab-scale prototype fabrication to commercial-grade production requires unidirectional die pressing or isostatic pressing to achieve the desired shape and products. Both pressing methods can be automated to a high degree and are used at optimum pressure in the mass production of bricks, slide gate plates, nozzles, and several shapes by the uniaxial press, and shroud, monoblock stopper, and submerged entry nozzle by the isostatic press, respectively. Uniaxial pressing is the most used ...