Mold strength

This is a measure for the strength properties of the compacted mold at room temperature (s. Green compression strength, Green tensile strength) and thus a measure for the quality of bentonite-bonded mold material mixture. It is substantially influenced by the binder content and the conditioning methods. And, the interdependence with the water content must always be taken into account.

With constant compaction intensity (s. Compaction) and binder quality, the strength properties are determined by the binder and water contents.

The conditioning factor specifies by which rate bentonite is capable of absorbing the added water in a mold material mixer and building up a binder film around the grains of the molding material. Optimum utilization of the strength potential of foundry bentonite is only achieved by complete coating of the quartz grains of the molding material with binder. Consequently, this increase in mold strength achieved during conditioning is a quality criterion for the conditioning factor of a bentonite material.

However, during optimization of the mold material quality, it must always be taken into account that increased binder contents will increase the costs for mold materials, have a negative effect on the sintering properties of the molding material, and impair stripping, i.e. separation of the solidified castings from the mold.

The green strength properties (Green compression strength, Green shear strengthGreen tensile strength, and Green cleavage strength) are determined by means of a standardized, cylindrical test specimen, which is compacted by three driving strokes (corresponding to a work of compression rate of 3.26 Nm) (s. Mold sand testing).

Additional references:

Mold strength tester
Mold material solidification
Mold material control
Mold material compaction
 

 

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