The second foundry, which utilizes automatic matchplate molding with proper mulling
, upped its levels of Western Bentonite by about 20%.
Through the testing, Hydrobond was shown to improve mulling
times and efficiencies, resulting in higher green strength, lower moisture contents, higher green tensile strength, lower sand friability and lower dry strength.
Between 120-160F, mulling
produces sand that is inconsistent and difficult to control.
If the return sand system does not adequately cool and hydrate the hot, dry shakeout sand, then even the best mulling
will have a difficult time creating somewhat uniform clay hydration.
The AFS clay composite undergoes agglomeration with the MB clay during final mulling
The total time the water is in contact with the premix and sand is called the "true mulling
This clay addition requires increased mulling
time, which can not be accomplished effectively in many high production sand systems.
Once clay balls exist in system sand, repeated recycling and mulling
increases the size of the clay ball.
Typical green sand system practice consists of molding, assembling and closing, pouring, cooling, shakeout, metal and refuse removal, cooling, storage, mulling
with water, adding bentonite and seacoal or cereal, and returning the sand mixture to molding.
Based on the success of NN-based control to arc furnaces, a project was initiated to investigate applications for green sand mulling
Critical to proper sand preparation, mulling
requires a careful understanding of the process' place in the entire sand system.
This is not necessarily a problem, but it can be associated with brittle sand, since this sometimes occurs with insufficient mulling
due to a high influx of core or new sand and bond.
The degree of mulling
also influences permeability because it affects the distribution of the clay and additives on the sand grain.
For a true study of the test, it was decided the sample variation should be minimized by added mulling
for better homogeneity of the sand.
Our speedmullors use a dynamic mulling
principle to keep the sand in constant motion.