MIŠTEROVÁ Hedvika UWB in Pilsen

The Potential of Steels with High Content of Vanadium and Chromium Produced by Powder Metallurgy for Processing by the Mini-thixoforming

Co-authors JIRKOVÁ Hana, AIŠMAN David, MAŠEK Bohuslav

Thixoforming is a method of metal processing by forming between solid and liquid states. Mini-thixoforming was developed especially for production of small components. With this method, the components can have complex shapes and the size of several millimetres. Until now, in metal processing research, there have been used metals with a wide temperature interval between solid and liquid states. Ledeburitic steels are one of the representatives of this group. After the thixoforming process, the structure of the component becomes polyhedral units of austenite which are bounded by a carbide network. Based on the hypothesis and calculations, mini-thixoforming have been made with three steels with various content of carbon, chromium and vanadium - CPM 15V, CPM S 30V and K190. These steels have the potential to achieve unusual structures. The content of vanadium is between 4 and 14.5%. The highest percentage of carbon is found in the steel CMP 15V – 3.4%. The disadvantage of these steels is an extremely small temperature interval for thixoforming processing. Because of the high sensitivity to the fast formation of the liquid phase, it was necessary to ensure suitable heating conditions. The differences between the structures depend on the content of carbon. In the high-carbon steel CPM 15V carbides of vanadium remained, but in the other steels a typical carbide net was created which bounds the polyhedral formations of MA components. The value of hardness is between 460 (CPM S 30V) and 800 (CPM 15V).