The master‘s thesis deals with the influence of the thermal cycle of welding with preheat on castings made of grey cast iron to change the hardness. The thesis deals with the classification of graphitic cast irons, their structure, properties and influences they have on the formation and transformation of the structure. Emphasis is placed on chemical composition and structure stability at elevated temperatures. The practical part deals with the investigation of the effects of casting repair on the decrease of hardness measured in the foundry Heunisch Brno.

The main target of this thesis is to choose the suitable hard filled wax for the invest-ment casting foundry Fimes a.s. There are several suppliers of these waxes in the World and in this work waxes of the most reputable suppliers from Europe have been investigated. During these tests there were mainly technological properties of the waxes and also dimensions of both wax patterns and also the final castings measu-red. Suitability of the tested waxes, their technological characteristics, analysis of di-mensions and finally basic economical calculations have been then used in this the-sis as a tool for the recommendation for the most suitable wax for the Fimes foundry.