This study was carried out to determine the effects of number of washings, curing time and heat treatment on the breaking strength of no-bake chromite sand-furan resin cores.

The Hevi chromite sand produced by a single stage washing of chromite sand was found to exhibit lower breaking strength in service. Forty five samples of no-bake chromite sand mixes were prepared with furan resin at room temperature and 39% humidity from chromite sand washed in single and two stages and cured at 2, 4 and 24 hours. Eighteen of the samples washed in single and two stages were tested for breaking strength without heat treatment, while the 27 obtained from single stage washing sand mix were heated to 900 oC and held at 12, 14 and 16 minutes before cooling. Re-washing gave an appreciable increase in breaking strength only for samples cured for 24 hours. The results obtained showed that highest breaking strength occurred in heat treated and cured samples with the highest occurring at curing period of 24 hours and 900 oC with holding time of 16 minutes. For re-washed samples held in room atmosphere, there was a decrease in breaking strength compared to the single stage washed samples. The implication of this work is that Hevi chromite sand has better breaking strength when heat treated at 900ºC and held in the temperature for 16 minutes. Evidently, the air cured samples may have been affected by the air humidity.

Key words: Chromite sand, Cores, No-bake, Curing, Strength.

Download: pdf

< Prev     Next >