Analýza defektního kovaného bloku z nástrojové oceli

Abstract

This diploma thesis deals with microstructure analysis of defective forged block made of 40CrMnNiMo 8-6-4 tool steel made by conventional technology. It was delivered in a refined state and showed no signs of internal damage with standard ultrasound control. Part of the block was broken during cutting. To determine the causes of this defect, the broken segment was subjected to metallographic and fractographic analysis. There were revealed areas of material inhomogeneities leading to a fragile breach of the forged piece. Supplementary microanalytical analysis was performed on samples taken from the block cutting surface. This analysis showed that the formation of heterogeneous regions in the volume of the material is due to local changes in the chemical composition. These areas were enriched with alloying elements, especially chromium and manganese.