Abstract
On the example of fracture of bars from vacuum melting steel with the established value of coercive force “10864” the requirements of technical specifications defining their properties and chemical composition are analysed. One of the mechanisms of bismuth ingress into vacuum melting electrical steel is revealed. One of the mechanisms of bismuth ingress into vacuum melting electrical steel is revealed. It is shown that the requirements of technical specifications for the supply of “10864” vacuum melting steel do not contain requirements for the maximum content of a number of impurities, in particular, bismuth. This means that when checking the chemical composition of the material of bars with end samples in accordance with the state standard of the Russian Federation № 7565, such impurities may not be detected simply because their content in accordance with the technical specifications, it is not checked. It is also stated that the requirements of technical specifications and reference documents do not allow the supplier to present the material with layers of bismuth, if they are detected with the use of magnifying devices, and have not yet led to the formation of cracks, which leads to the need to introduce additional requirements for the chemical composition and structure of the material of bars from steel “10864” vacuum melting in contracts for the supply of material.
Keywords:
steel, bars, parts, electrovacuum devices, temperature, impurities, bismuth, macrostructure inspection.