ARCHIVES of FOUNDRY ENGINEERING DOI: 10.1515/afe-2015-0029 Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences ISSN (2299-2944) Volume 15 Issue 2/2015 13 – 16 ARCHIVES of FOUNDRY ENGINEERING Volume 15, Issue 2/2015, 13-16 13 Increasing of Utility Properties of Grey Cast Iron Castings with Heat Treatment Š. Eperješi a *,J. Malik a , I. Vasková a , D. Fecko b a Department of Metallurgy Ferrous and Foundry, Faculty of Metallurgy, Technical University in Košice, Slovakia b Foundry SEZ Krompachy a.s., Slovakia *Corresponding author. E-mail address: stefan.eperjesi.2@uke.sk Received 23.02.2015; accepted in revised form 31.03.2015 Abstract Grey cast iron belongs to materials for casting production, which have wide application for different industry branches. Wide spectrum of properties of these materials is given by the structure of base metal matrix, which can be influenced with heat treatment. Processes of annealing can be applied for grey cast iron without problems. During heat treatment processes, where higher cooling rates are used, the thermal and structural strains become important. Usage and conditions of such heat treatment for grey cast iron castings of common production are the subject of evaluation of this article. Keywords: Grey cast iron, Heat treatment, Hardening capacity, Austenite, Martensite 1. Introduction Grey cast iron belong to the oldest and most used metal materials for casting production. They have good foundry properties and with continuous improvement of production technology they have achieved also suitable utility properties which have shown with increased of technical level and working reliability of castings. Present knowledge achieved from studies of isothermally improved or anisothermally worked steel and iron shows advantageous strength and plastic characteristics of bainitic structures and also increased wear resistance. In alloys with suitable chemical composition it is possible to achieve bainitic structure also with conditions of fluent cooling, e.g. in air, using directional cooling or cooling in a mould [1]. From the point of view of practical application this is the easiest way of heat treatment. With anisotropic breakdown of austenite mostly complicated structural mixtures with significant ratio of martensite is created and therefore the final properties of casting are being achieved with following tempering. In comparison to steel, the relations between properties and structure of cast iron were less examined. Significant turnover was showed in last years, mainly with increased usage of ductile cast iron. 2. Heat Treatment of Graphitic Irons by Refinement From the point of view of maximal productivity and effectiveness of production it would be best to produce the cast iron castings without the need for heat treatment. Grey cast irons are not very often heat treated. It is due to the fact, that with heat treatment we are not able to change the shape and distribution of graphite (although the graphitization degree is partially being changed), we can influence the basic metal matrix [2]. According to this, we can significantly change the hardness, partially the tensile strength, but due to the shape of graphite we cannot practically influence the low toughness of grey cast iron. Mechanical properties and wear resistance in grey cast iron