What is AFS clay?
AFS clay is the percentage of particles with a diameter less than 20 microns in a foundry sand sample. This includes active clay, dead clay, silt and inert fines.
What is active clay and dead clay?
AFS clay contains active clay, dead clay, coal dust, and other materials that float or dissolve in water. This test indicates the total water absorbing materials in the system. Out of all the materials, only the active clay part gives the sand bonding capacity. Chemically active clay – Methylene Blue Clay.
What are the important properties of sand testing?
A basic set of parameters to test are:
- Fineness number (grain size/AFS Number) of the base sand.
- Moisture content in the mixture (ranges from 2-7% depending on the casting method)
- Permeability (ability of compacted mould to pass air through it)
- Total clay content (dust content)
How is AFS number calculated?
This number is calculated from the size distribution, which is determined by standard ASTM sieves. Each fraction is multiplied with a weighting factor, the results are added together and divided by 100. Note that the resulting AFS number gets bigger as the average size decreases.
What is Loi of sand?
LOI is the weight change percentage caused by heating the sample to high temperature and is used to give a measure of the extent of volatile substances. The original use of this test was to estimate the amount of coal dust in recycled foundry sand.
Why is it required to estimate the clay content of the molding sand?
Moulding sand may contain 2 to 50 percent of clay this is responsible for bonding and particles together. Clay influences strength , permeability and other moulding sand properties. Clay Tester measures the amount of live clay present by determining the Base Exchange capacity of the clay.
Which type of Moulding sand is preferred in machine Moulding?
System Sand
System Sand: The sand employed in mechanical heavy castings and has high strength, permeability and refractoriness, is known as system sand. It is used for machine moulding to fill the whole flask. In machine moulding no facing sand is used. The system sand is cleaned and has special additives.
What is AFS in sand?
A standard parameter to express the size of molding sands is the AFS fineness number (AFS = American Foundry Society). This number is calculated from the size distribution, which is determined by standard ASTM sieves. The AFS number is considered proportional to the number of grains per unit weight.
How do you find AFS grain fineness number?
AFS fineness number which is the standard for reporting the grain size and distribution of sand was used to assess the particles [11]. This was applied to the sieve result as in Table 6 to obtain the AFS number. From the table, grain fineness=total product\% sand substance = 3241\100=32.4. …