Predicting Core Gas Defects with FLOW-3D Cast

Figure 1: Spatial plot of core gas pressure and core gas surface flow
to metal at 5 sec. A two internal core assembly was bottom filled
in the simulation in 1.5 sec. The gas pressure in the saddle core
is roughly double what it is in the T-core. The vertical drill in the
T-core along with one T-core print is very effective in venting all
the T-core binder gas. The saddle remains inadequately
vented in this design.

Modeling Castings with Cores

Chemical binders in the sand can produce gas when heated by the molten metal and if not vented adequately, the gas may flow into the metal resulting in a gas porosity defect. This is most likely with cores that form thin interior features of castings that heat up quickly and have long venting paths. The core gas model in FLOW-3D Cast predicts the possibility of such gas defects and helps design core venting that can safely evacuate all the binder product gas from the cores.

Related links:
Predicting Defects with the Core Gas model

Casting Better Parts by Detecting Porosity with FLOW-3D Cast's Core Gas Model
TN 84 | Binder Gas Generation and Transport in Sand Cores and Molds
Read more in our Casting Tech Papers

Modeling Defects in Aluminum and Iron Castings

The Core Gas model predicts defects for resin-bonded cores both in iron castings (Fig. 1) and in aluminum castings (Fig. 2). It works concurrently with filling and solidification models in FLOW-3D Cast and computes binder gas generation and flow during and after the end of casting fill.

             
Figures 2a and 2b: Filling of an open flask partial V8 Al block assembly. The two cores form the
water jacket cavity of the block. The flask is bottom filled with Al in 20 seconds (Fig. 2a) and
the water jacket core when unvented blows gas into the metal during fill (Fig. 2b).

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