by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
button in toolbar for more information.
Metal Casting Technologies : March 2009
solid shell around bolts and surface of mold, contraction increases and contraction load overcomes expansion load, thus when the time and load are corresponding 5480 C and -784N, c graph moves to positive axis. At 5360 C consequent of the pressure load and the extension load converting to extension load. Extension load applies to hot spot, if conditions are proper hot tearing occurs. After knock-out see visible crack on the casting surface. Optical micrographs of casting (Figure 5) confirm inter dendritic crack and other hot tearing characters described in introduction. In the Figure 3 don’t see any peak, may be peak of hot tearing eliminated in expansion load. In order to study this occurrence second test designed. In the second test copper block are jointed to bolts to minimize expansion and increase heat transfer of mold material in the end of casting arms. This act causes increasing rate of applied strain on the hot spot. Figure 4 show reduce negative load. This is a good result and increasing accuracy of apparatus. Due to change arms mold material, direct solidification occurs and solidification front moves rapidly from arm to center of casting, in this stage hot spot transfer to foot (Figure 1) and out of stress region. So hot tearing does not occur in the previous region. Other experiments with other alloys uphold accuracy of apparatus. Conclusions In this study new apparatus has been made to enable a quantitative investigation of hot tearing. By this apparatus even while the new apparatus does not have any peak or visible occurrance of cracks, the hot tearing susceptibility of different alloys can be compared. Hot tearing susceptibility can be determined by a count of strain rate in the mushy zone and can also be determined by the occurrence of temperature and solid fraction in hot spot. The accuracy of this apparatus can be compared with another method using a load cell, however its use and its usage are very simple and do not need special experience. ¦ Reference 1 J.B. Mitchell, S.L. Cockcroft, D. Viano, C. Davidson and D.STjohn, ‘Determination of Strain during Hot Tearing by Image Correlation’, Metallurgical and Materials Treansaction A, 38A, pp.2503-2512, 2007. 2 X. Li, Ph.D Thesis, Universite Du Quebec A Chicoutimi, May 2000. 3 Beeley, Peter R, Foundry Technology, 2001, Butterworth Heinemann. 4 Shan Lin, Ph.D Thesis, Universite Du Quebec A Chicoutimi, Fevrier 1999. 5 D.G. Eskin , Suyitno , L. Katgerman , Mechanical properties in the semi-solid state and ot tearing of aluminium alloys, Progress in Materials Science 49 (2004) 629–711. 6 C. Monroe, C. Beckermann, ‘Simulation of Hot Tearing and Distortion During Casting Of Steel’ , The University of Iowa. 7 C. Davidson, D. Viano, L. Lu and D. StJohn, Observation of Crack Initiation During Hot Tearing, International Journal of Cast Metals Research, VOL 19 NO 1,2006,pp 59-65. CASTAL DESIGN ZINC CASTERS By the end of 2008 three zinc alloy strip casters have been commissioned in two European countries CASTAL ENGINEERING Continous casting technologies 18 Hippocrates Street, 145 63 Kifi sssia, Greece Phone: + 30 210 8073088 Fax: +30 210 8070367 Mobile: +30 697 2022162 Email: firstname.lastname@example.org Web: www.castal.gr METAL Casting Technologies March 2009 45