Perfection of the equipment of electromagnetic stirring in moulds of billet and bloom CCM

Abstract

To avoid defects of continuously casted billets, such as core porosity, shrink liquation, ingot developed dendrite structure and others, various methods of external physical impact on the crystallizing billet are used. One of the most technological and effective of them is the electromagnetic stirring (EMS) of the liquid melt of the crystallizing billet. An analysis of the experience of industrial EMS systems application at steel plants of Russia was accomplished. It was noted, that operating in Russia industrial CCM, intended for production of high quality billets, are equipped mainly by EMS systems of foreign production. The stator of the EMS is located outside a mould body and the bodies of the stator and the mould are manufactured of nonmagnetic steel of austenite class. Such systems are characterized by low reliability and high energy consumption because of their design features (location outside a mould body and necessity to use for them a separate circuit of cooling by a “boiler” water). Bessides, most of the EMS stators of foreign manufacturing are made in nonseparable bodies, hence in case of a failure the expensive rrepair of the stators should be carried out at the foreign plants-manufacturers. At present in Russia the EMS systems are being elaboorrated by specialists of AKKH “VNIIMETMASH”, Moscow. VNIIMETMASH within the frame of import substitution program elaboorated both built-in and external variants of EMS systems for moulds of billet and bloom CCM, the stator coil poles being cooled bby the water of the mould and its winding is made of immersible into water wire with a double insulation. Based on the results of thee study it was determined, that location of the elaborated EMS systems in a mould results in improving of the surface quality, as welll as quality of the subsurface layer and the billet macro-structure, decreasing of the point unevenness and decreasing of number of thee subshell bubbles.