Livarski vestnik 57 / 2010 št. 4
Horáček Milan, Roučka Jaromir
LATEST RESEARCH ACTIVITIES AT THE BRNO UNIVERSITY OF TECHNOLOGY RELATED TO THE INVESTMENT CASTING PROCESS
Gorazd Lojen, Albert C. Kneissl, Mirko Gojić, Rebeka Rudolf, Miodrag Čolić, Ivan Anžel
CONTINUOUS CASTING OF Cu-Al-Ni SHAPE-MEMORY ALLOYS
Hans Roedter, Martin Gagné
MICROSTRUCTURE DEFECTS IN HEAVY SECTION DUCTILE IRON CASTINGS –FORMATION AND EFFECT ON PROPERTIES
Latest Research Activities at the Brno University of Technology related to the Investment Casting Process
The technology of investment casting has been studied and research in this area provided at the BUT for some time and results published at different conferences and foundry journals [1, 2, 3, and 4].
In this article the latest research activities focused to the still growing “net shape” technology of “lost wax process” or more often used term “investment casting technology” will be described. There are several groups of researchers at the BUT working on different topics which are listed below (together with the groups´ leader e-mails):
Rapid Castings by FDM RP + Investment Casting Technology, horacek@fme.vutbr.cz
Thermal processes in pouring into ceramic shells, roucka@fme.vutbr.cz
Ti – Al alloys for High-Added-Value Castings, zemcik@fme.vutbr.cz
In this article the latest research activities focused to the still growing “net shape” technology of “lost wax process” or more often used term “investment casting technology” will be described. There are several groups of researchers at the BUT working on different topics which are listed below (together with the groups´ leader e-mails):
Rapid Castings by FDM RP + Investment Casting Technology, horacek@fme.vutbr.cz
Thermal processes in pouring into ceramic shells, roucka@fme.vutbr.cz
Ti – Al alloys for High-Added-Value Castings, zemcik@fme.vutbr.cz
Gorazd Lojen, Albert C. Kneissl, Mirko Gojić, Rebeka Rudolf, Miodrag Čolić, Ivan Anžel
Continuous Casting of Cu-Al-Ni Shape-Memory Alloys
Povzetek
Shape memory alloys, especially polycrystalline ones, have some disadvantages compared with the most used Ni-Ti alloys. The most important disadvantage is high brittleness, and consequently, smaller reversible deformation. But on the other hand, Cu-Al-Ni alloys have also some advantages: melting, casting, control of chemical composition and machining are less demanding, they have higher Young’s moduli, higher resistance to degradation of functional properties and better cost-to-effect ratio. But working of slabs and ingots into semi-products of smaller cross-sections, even hot working (brittle β intermetallic phase), is still work and time consuming and thus expensive since only a small degree of deformation without intermediate annealing is possible during the rolling or drawing process. Therefore, manufacturing semi-products of smaller cross-sections directly from melt could considerably lower the costs. In spite of that, no data on the high-productivity continuous casting process of small-cross-section of shape-memory-alloy rods or strips could be found in references. Our research should diminish this blank. In our first experiments Cu 13 % Al – 4 % Ni (mass fractions) shape-memory alloy was continuously cast with laboratory equipment for vertical continuous casting directly from the melting crucible. A graphite mould with diameter of 16 mm was applied and various combinations of casting parameters were tested. Average casting velocities were in the range from 250 to 625 mm per minute. Castability of the alloy appeared to be good with all the tested parameters. This paper presents also achieved surface qualities, microstructures and some mechanical properties of cast strands.
Keywords: Shape-memory alloys, Cu-Al-Ni, Continuous casting, Microstructure, Mechanical properties
Keywords: Shape-memory alloys, Cu-Al-Ni, Continuous casting, Microstructure, Mechanical properties
Microstructure Defects in Heavy Section Ductile Iron Castings –Formation and Effect on Properties
Povzetek
Ductile Iron exhibits a range of mechanical properties that makes it suitable for light weight as well as heavy section castings. However, these properties are sensitive to microstructure defects whose characteristics and occurrence are, in some cases, related to the casting size. For example, defects such as chunky graphite, intercellular segregation defects and dross, although not exclusively found in heavy section ductile iron castings such as wind turbine components, exhibit a significantly higher probability of formation as the casting size/modulus increases. In this paper the occurrence and effect on properties of these three types of defects typically found in large ductile iron castings are described and their mechanisms of formation discussed. Based on these observations, remedies to eliminate/limit their formation are proposed.