The procedure of shell making goes as follows:
1.Immerse the cluster of wax moulds into the surface coating paint;
2.Lift the cluster, wrap with quartz sand with diameter 40-70 meshes and submerge it in the induration water consisting of Ammonium Chloride for 10-20 minutes;
3.Hang it for drying for about 40 minutes;
4.Immerse it into the reinforce coating paint;
5.Wrap it with rough sand with diameter 20-40 meshes and submerge it in the induration water made of Magnesium Chloride for more than 50 minutes;
6.Hang it for drying for not more than 30 minutes;
The 4th and 5th steps should be repeated several times to reinforce the shell until the sand shell is strong enough. Ammonium The concentration of Ammonium Chloride is 17%-22%. The 1.0-1.1 densimeter is used to measure the density once a week. Magnesium Chloride is used for the induration of reinforce layer. The density is 1.22-1.24. The 1.2-1.3 densimeter is used to measure the density every three days.
Dewaxing: Lay the cluster with the sand shell on the floor for more than 12 hours before dewaxing so that the shell is firm enough. Hot water with 3-5% Ammonium Chloride and 0.15% industrial hydrochloric acid in it is used to get rid of the wax. Before dewaxing, the sand and the coating paint on the pouring basin and gate stick should be cleaned. Clusters of moulds are put into the hanging basket and submerged into the hot water which is 95-98℃ hot. The dewaxing time varies from 30-50 minutes according to the required product technique. Get the gate stick out when the gate stick and the wax are separated. Raise the hanging basket and meanwhile shake the basket so that the water flows out of the shell and into the dewaxing basin. Next put the dewaxed moulds in a specified area in terms of steel designation. The basin is cleaned of sands and replaced with new dewaxing water every 10 days.