Developing a technology for production of bottom blocks with a low modulus of elasticity

Abstract

The need for substantiated formulation of quality requirements for cathode blocks is emphasized. The ratio of the bending strength to elasticity modulus is proposed as a criterion for evaluating the strength properties of blocks. Techniques for improving this ratio in the production of carbon graphite materials are discussed.The operational reliability of cathode blocks is determined by their physicomechanical properties which, in turn, are specified by the corresponding technical documentation. Over the past 5 years, requirements placed on cathodes blocks have time and again been revised, which finally resulted in a poorly substantiated and somewhat relaxed margin of performance. As shown by practice, formal conformance with the specifications placed on cathode blocks is not necessarily a guarantee of their reliable performance. The strength properties of cathode blocks have been and continue to be one of the most debatable and controversial issues.In deciding on which of the strength characteristics is most informative, the reasoning is usually based on the concept of the weakest link.The strength characteristics of carbon graphite materials are typically arranged in ascending order tension -bendingcompression, that is, the weakest link is tensile strength. However, according to reported data [1], viewed technologically, tensile strength is a less sensitive feature than bending strength in the preparation of carbon graphite materials (for example, in regard to the amount of pitch added). The low sensitivity of tensile strength to central technological parameters (such as porosity or specific electric resistance) may be due to imperfectness of the method (diametral compression) used for determining this strength characteristic. Thus, the bending strength has been recognized to be the best informative index for evaluating strength properties of cathode blocks. A similar opinion was also voiced in [2] on the grounds that this parameter gives a measure of the resistance to buckling and shear stress.A still fuller evaluation of the strength properties of blocks is the ratio of the strength to the elasticity modulus considering that this ratio characterizes the maximum permissible strain to failure of the material. Based on the previously reported data [3], it has been decided on taking the ratio of the bending strength to the dynamic modulus of elasticity as the best informative evaluation of maximum permissible strain of graphite materials. The higher the ratio, the higher the ability of a material to sustain loading conditions; the ratio can be made higher either by increasing the bending