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| Gedeonová Z., Dúl J., Ballók P., Ševcová M. |
| METALLURGICAL QUALITY AND VOLUME CHANGES DURING SOLIFIDICATION OF SPHEROIDAL GRAPHITE CAST IRON |
Abstract
The volume and linear changes of castings including inner shrinkage cavities during the solidification are affected by the cast metal properties and by the given mould as well. The observation of this effect is especially important at founding of graphite cast iron, i.e. at spheroidal graphite (SG) and flake graphite (FG) iron castings, while during the solidification of these castings an increase of volume is at present crystallisation of graphit-austenit eutectic.
Realized experimental measurements (with SG cast iron samples) have confirmed the fact, that linear changes during the solidification consist of two periods. In the first period positive, negative, or almost no linear changes were measured. In this period linear changes depend on properties of filer, binder and rigidity of mould jacket. Autors already have concerned with analysis of influence of mould properties on dimensional changes of graphite cast iron, see [1-4].
Second period of dimensional changes, which begins by eutectic crystallisation of casting, was always positive following graphitic expansion, i.e. there was increasing of dimesions. Seemingly, one has been a little effected by mould properties (destruction of binder system is already in progress) and rigidity of mould jacket, but has been destinated by metallurgical quality of melt significantly. Relationships between selected metallurgical quality indicators, such as eutectic degree Sc, dimensional characteristic D2 also temperature characteristic RU and tgß and resultant casting properties, show markedly coherence mainly with the volume of shrinkage cavity Vst (%) and graphite nodule count per mm2 in the structure.
From the analysis of dimensional changes during the solidification of cast iron with spheroidal graphite followed that we can control first period of dimensional changes only by mould properties. In the second period, when the eutectic graphitization of casting is in the progress, we can control the generation of shrinkage cavity only by metallurgical quality of solificated metal.
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| Keywords: spheroidal graphite cast iron|solidification|dimensional and volume changes|metallurgicalquality| |
| No 3 (2000), p. 202-213 |
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| Kvačkaj T., Pokorný I., Vlado M. |
| SIMULATION OF FORMING PROCESSES BY TORSION TESTS |
| Keywords: flow stress|torsion test|hot workability|electrotechnical steel|low carbon steel|structural development|static recrystallization| |
| No 3 (2000), p. 242-248 |
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| Bednarczyk J., Głuch G. |
| ELECTRODYNAMIC METAL FORMING |
| Keywords: electromagnetic forming of metals|high velocity forming|high energy-rate forming| |
| No 3 (2000), p. 270-278 |
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