Through analysis, the main reasons for the air hole defects on the surface of the driving wheel are that the air volume of the coated sand core increases, the wall thickness of the nodular cast iron is thin, and the exhaust is poor. In order to solve the blowhole defect, the following improvement measures have been taken:
(1) 50/100 coarse sand is used for 1 # and 2 # coated sand cores to reduce the gas generation of sand cores.
(2) The assembled 6 # sand core is put into the drying furnace for drying, and the process parameters are set as the holding temperature of 180 ℃ and the holding time of 4 h.
(3) Increase the exhaust passage, as shown in the figure. After implementing the improvement measures, more than 120 ductile iron castings of driving wheels were produced, and the defects of air holes were eliminated, and the surface quality was good.
