Abstract
The paper presents results of analysis of literature data and own researches in the field of the austempered high-strength cast irons with spherical and vermicular graphite. Difficulty of control and identification of needle (bainite and martensite) and non-needle (troostite) quenching structures is noted. The basic methods of control of quenching structures are considered. 12austempered compacted graphite iron samples have been investigated to find reliable criteria for identification of quenched structures by methods available to production metallographic laboratories. The results of microstructural analysis (using light microscope) of several hundred fields of view and several hundred measurements of microhardness by Vickers method have been analyzed. It is found that the use of light microscopy and microhardness determination of the austempered compacted graphite iron matrix separately does not give reliable identification of hardened structures. It is established that combination of these methods is the best solution of the problem of qualitative control of the hardening structures of cast irons under production conditions. On the basis of the conducted research a method of checking and identifying the hardening structures of the austempered high-strength cast irons is proposed, which consists in comparing the results of microhardness measurement with microstructure areas that can be used using the equipment available in the production laboratory.
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