Influences of Rod Diameter and Sand-Mould Strength on Hot Tearing in Mg WE43A Constrained Rod Castings

Under conditions of changing sand-mould strength and rod diameter, hot tearing susceptibility of Mg WE43A alloys was studied using constrained rod casting solidified in a sand mould. Variations of temperature and shrinkage force with time during solidification of Mg WE43A alloy were recorded by means of a thermocouple and a force sensor. Susceptibility to hot tearing at hot section was decreased with increasing rod diameter from 10mm to 20mm. The rod with 10 mm diameter fractured, and the rod with 15 mm diameter presented hot tearing. No hot tearing was noted for the rod with 20 mm diameter. For the resin content of 1%, 1.5%, 2%, 2.5% and 3%, the tensile strength of sand mould was measured as 0.12, 0.18, 0.28, 0.17 and 0.15MPa, respectively. The casting fractured at hot spot position for the sand mould with strength of 0.12MPa. Hot tearing occurred at hot spot for the sand mould with strength of 0.15MPa. No hot tearing was found at hot spot for the sand mould with strength of 0.28MPa. The present research confirms that increasing the sand-mould strength and avoiding the entrapment of sand particles and the formation of gas pores during casting increase the resistance to hot tearing.