Core gasses

Gas that originates during casting in connection with air and the added binders, additives and facing coats.

These core gasses must be properly vented through core prints to avoid occurrence of gas blister defects and thus production of rejects (s. a. Core venting).

Gas development from organically bound molding materials (see Organic binder systems) is illustrated in a schematic diagram in Figure 1. Figs. 2 and 3 illustrate the development of gasses (gas quantity) and the gas surge (gas release rate) using the examples of various core mold materials.

  • Fig. 1: Mechanism of gas blister formation in organically bound core mold materials: I Boil-up of the gas blister; II Freezing of the gas blister; PG Gas pressure; PM metallostatic pressure; h metallostatic pressure value; t1 Start of casting, start of gas development; t2 Start of solidification; t3 End of solidification (Source: E. Flemming, W. Tilch: Formstoffe und Formverfahren (Molding materials and molding processes), Deutscher Verlag für Grundstoffindustrie, Stuttgart, Leipzig)
  • Fig. 2:  Gas development sequence of various core mold materials when heated up to 850 °C (gas quantity)
  • Fig. 3: Gas development sequence of various core mold materials when heated up to 850 °C (gas release rate)
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