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1
Content available The Influence of Lamellar Graphite Cast Iron Annealing on Hardness and Structure
Roučka J., Prochazka J., Kana V., Krutis V., Nedelova K.
Archives of Foundry Engineering
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2019
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iss. 4
105--112
EN
An analysis has been carried out of the influence of annealing time at the preheating temperature of 650 °C on the change in hardness and alloy structure of lamellar graphite cast iron in the working as well as in the laboratory conditions. This preheat temperature is common during reclaiming welding of castings with complex shapes. The changes in unalloyed cast iron EN-GJL 200 to EN-GJL 300 according to ISO 1690 standard and cast iron with low amount of elements such as Sn, Cu, Cr, and Mo and their combinations were assessed. It was found that the cast iron of higher strength grades has better hardness and structural stability. Cast iron alloyed with chromium or its combinations has the highest stability. In unalloyed cast iron, a partial degradation of pearlite occurs; in alloyed cast iron the structural changes are not conclusive.
2
Content available Prediction of Ferrite Content in Austenitic Cr-Ni Steel Castings During Production
Senberger J., Pernica V., Kana V., Zadera A.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 3
91--94
EN
Determination of the ferrite content in austenitic steels, which solidified under defined conditions. Ferrite content in austenitic matrix was determined from samples with wall thickness of 60 mm. Measured ferrite contents served to propose the regression equations for the calculation of the ferrite content in steels with Cr content of 18 up to 22 % and Ni of 9 up to 11 %. An additional regression equation was proposed for steels with a higher Ni content. The proposed regression equations have been checked up on the operating melts. In conclusion, the ferrite content in the axis of the casting of wall thickness of 500 mm has been calculated and it was compared to the ferrite determined in the usual way from the cast-on test.
3
Content available remote Influence of the cut direction through the semi-finished product on the occurrence of cracks for X210Cr12 steel using WEDM
Mouralova K., Klakurkova L., Matousek R., Prokes T., Hrdy R., Kana V.
Archives of Civil and Mechanical Engineering
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2018
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Vol. 18, no. 4
1318--1331
EN
Wire electrical discharge machining (WEDM) is a key technological process for the production of parts from semi-finished products to the final heat treatment as it also enables the machining of very hard material. The quality of an electro-erosive machined surface is a very important factor with regard to the consequent functionality and life cycle of the manufactured part. The occurrence of cracks or burned cavities is therefore an acceptable defect of the sub-surface area, which along with residual stress may lead to the destruction of the machining. This study deals with the influence of the cut direction through a semi-finished product on the occurrence of defects (cracks, burned cavities) regarding the influence of setting up the parameters of the machine (gap voltage, pulse on and off time, wire feed and discharge current) and the type of heat treatment of the material. In order to study the surface and sub-surface area of the machined samples, electron microscopy was used, including the use of the local EDX chemical analysis.
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