Developing Techniques for Testing Magnetic Properties of Electric Steels. II. Variations in Magnetic Properties and Their Effect on Reliability of Testing Results (review article)

The paper presents experimental data concerning the magnitude and character of variations in magnetic properties of electric steels (among a number of sheets, within one sheet, over the length and width of a roll, etc.). The paper also considers effects of variations in magnetic parameters of steel on the quality of fabricated components and reliability of measurements of steel parameters conducted in accordance with the existing State Standards by testing one selected sample cut from single sheets of a batch, or from the beginning or end of a roll on an Epstein's apparatus. The inhomogeneity of magnetic parameters is a natural consequence of the instability of the technological process of the steel manufacture on all its stages and on the stages of its transformation (chemical composition, smelting conditions in which slabs for rolling are produced, regimes of rolling and annealing, etc.), therefore these parameters usually obey the law of normal distribution. Feasibility of more efficient methods of steel testing designed to optimize and improve the reliability of testing results is discussed.