Developing techniques for testing magnetic properties of electric steels. I. Epstein's apparatus (review article)

The review briefly describes the history of development of techniques measu ring magnetic parameters of one of the materials which are of vital importa nce for energy generation, electric engineering, radio engineering, and oth er branches of industry, i.e., electric steel, whose quality determines ope rational characteristics of numerous devices, such as generators, transform ers, electric motors, magnetic conductors of relay switches in various auto mated systems, etc. The development of techniques for measuring its magneti c parameters is reviewed starting with the advent of Epstein's apparatus, w hich was designed at the turn of the century [1] and has remained an instru ment used in resolving controversies between suppliers and consumers of ele ctric steels, and ending on contemporary methods of testing roll steels usi ng complex electronic circuits incorporated in automatic control systems of factories. In connection with the spread of magnetic parameters of electri c steels (in sheets, rolls, and batches), the issues of standardization and selection of measures for more reliable characterization of steels are dis cussed. Instruments and facilities for classification and distribution of s teels in batches with uniform characteristics are also described. Sheet-testing instruments for measuring steel parameters, which are designe d to replace Epstein's apparatus, are described. Problems of on-line testin g of electric steel in rolls and instruments for such tests developed by th is time are discussed. In this connection, the issues of steel tests based on indirect characteristics [those not specified in GOSTs (State Standards) ], which could be more easily conducted on production lines, alongside the methods and facilities for nondestructive measurements of magnetic paramete rs are broached. Part I of the review is dedicated to conditions of magneti c measurements using Epstein's apparatus, and this paper was written exactl y one hundred years after its invention in 1900.