Grain Fineness Number (GFN)

• Grain Fineness Number (GFN) is the measure of the fineness of a given sand sample.
• It basically measures the average grain size of a given sand sample.
• Parameters affecting grain fineness number (GFN) of a sand sample are: metal type, temperature of pouring, product mixture of casting and required surface finish.
• After determining an optimal value for GFN, maintainence of consistency of the grain structure is the critical portion to be achieved.
• High GFN = Fine Sand = Low permeability leading to gas defects.
• Low GFN = Course sand = Metal penetration, rough surface finish, burn-in and burn-on.
• Since GFN just represents an average of fineness, sands with different distributions can have the GFNs

Sieve Shaker

• It is used for the size-based separation of different particles of the sand sample.

• The separation is performed by passing the sand sample through a series of sieves by the phenomenon of agitation.

• Sieve shaker can be of different types based on the sieve distribution and the level of automation.

• Average grains fineness number, GFN = Q/P

  where Q = sum of product of percentage sand retained in sieves and corresponding multiplier
  P = sum of percentage of sand retained in sieves