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 2010
METAL Casting Technologies March 2010 31 was fused at about 16000 C in an induction furnace. Basic lining was used and a graphite crucible was used for melting the slag. The melt was held for 8 minutes till foaming stopped and was poured into a preheated clay graphite crucible and was allowed to solidify. The slag mass easily comes out from the crucible. After cooling, the solidified slag is crushed, sieved and stored in a desiccator. ESR process The electrode was attached to the ESR unit. 900 grams slag was preheated at 8500C for 5 hours before charging into the mould to avoid any moisture pickup. ESR was carried out in a water cooled tapered mould of 85 mm base diameter, with electrode connected to DC positive power. A dummy mild steel starting block of 85 mm diameter was welded on the 2 mm thick steel plate. The hollow mould was assembled on this 2 mm thick steel plate. This plate was placed on the water cooled copper base of the ESR unit. The process was started by striking an arc between the electrode and the top surface of the dummy block. Once heavy arcing started the prefused preheated powder slag was added around the arc. The slag melted quickly and filled the space between the electrode and starting block, extinguishing the arc. There after the heating was due to the resistance of the molten slag to the passage of current. The remaining slag was added quickly and the process stabilized. The melting of the slag took 4 minutes. The slag was deoxidized by continuous addition of aluminium wire tied along the length of the electrode. The temperature of outlet water from the mould was 400C. The current and voltage during this process were in the range of 750 - 770 Amps and 25 -- 30 V respectively. Water flow rates to the mould and base were kept at 35 & 20 litres/minute controlled by the rotameters. Figure 3 shows the set up of the ESR unit. After the ESR process, the ingot was easily removed from the mould. Characterisation The ingot was cut from the top for chemical analysis. The rest of the ingot was used for the preparation of mechanical testing and microstructure specimens. Rockwell hardness values were taken on C scale. Charpy impact test was carried out at room temperature. Tensile tests were carried out at room temperature at a cross head speed of 1 mm/min.
Media Kit 2010