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Crystallization of GX2CrNiMoCuN 25-6-3-3 Grade Alloy Cast Steel and its Microstructure in the As-cast State and After Heat Treatment

Wróbel Tomasz, Jurczyk Paweł, Baron Czesław, Nuckowski Paweł M.

Archives of Foundry Engineering

2023

Vol. 23, iss. 3

94--103

The paper presents the results of research conducted in the field of crystallization and microstructure of duplex alloy cast steel GX2CrNiMoCuN 25-6-3-3 grade. The material for research was the above-mentioned cast steel with a chemical composition compliant with the relevant PN-EN 10283 standard, but melted at the lowest standard allowable concentration of alloying additives (some in short supply and expensive), i.e. Cr, Ni, Mn, Mo, Cu and N. The analysis of the crystallization process was performed based on the DTA (Derivative Thermal Analysis) method for a stepped casting with a thickness of individual steps of 10, 20, 40 and 60 mm. The influence of wall thickness was also taken into account in the cast steel microstructure testing, both in the as-cast state and after solution heat treatment. The phase composition of the cast steel microstructure was determined by using an optical microscope and X-ray phase analysis. The analysis of test results shows that the crystallization of tested cast steel uses the ferritic mechanism, while austenite is formed as a result of solid state transformation. The cast steel under analysis in the as-cast state tends to precipitate the undesirable σ-type Fe-Cr intermetallic phase in the microstructure, regardless of its wall thickness. However, the casting wall thickness in the as-cast state affects the austenite grain size, i.e. the thicker the casting wall, the wider the γ phase grains. The above-mentioned defects of the tested duplex alloy cast steel microstructure can be effectively eliminated by subjecting it to heat treatment of type hyperquenching.

The impact of the melting and pouring process on the quality of the biggest rocking bell called Vox Patris

Bartocha Dariusz, Baron Czesław

Quality Production Improvement - QPI

2019

Vol. 1, Iss. 1

230--237

The paper describes the process of melting, metalworking and pouring the form of the world's largest 55-ton rocking bell called Vox Patris. The project was carried out by Pracownia Ludwisarska of Jan Felczyński from Przemyśl in cooperation with Rduch Bells & Clocks from Czernica and Metalodlew SA from Kraków. Comprehensive scientific and technical support of the project was provided by the Department of Foundry of the Silesian University of Technology. The bell is made of bronze, which is an alloy of copper and tin with a content of tin at the level of 20%. The foundry, where the melting and pouring process took place, had two 14 ton electric furnaces, 15 ton transport pouring ladle and a 60 ton collection ladle. Therefore, it was necessary to determine the minimum temperature of the pouring and the conditions for holding the liquid metal so that the metal from the first cast would not solidify before accumulating its total amount (four melts) (Bartocha and Baron, 2015; Bartocha and Baron, 2016). The study presents the tests of alloy properties and a series of computer simulations. Thanks to them the maximum and minimum permissible temperature of metal overheating has been determined (Bartocha, 2017). The final stage of the cast was the mold pouring process. The filling system was responsible for the correct performance of this process. This system comprised a tank (collector) under a doublestopper 60-ton main ladle, an elevenmeter tapping spout, an infusion tank and a downgate. The task of the gating system is uniform and continuous supply of liquid metal to the mold until it is completely filled. The unusual layout, that was used, required checking many factors. Various configurations of the system parameters have been tested based on the series of computer simulations (Czochlarski and Bukowski, 1935; Ignaszak, 1999).