Following sand testing are used in foundry.
Moisture Content Test: To find the moisture content in sand, moisture teller equipment is used. It consists of cast iron pan and an infrared heater bulb fitted in a shade. Twenty grams of sand is taken in a pan and it is exposed in infrared heater for 2–3 min. Difference in weight is found (i.e., weight before drying and weight after drying), which shows the amount of moisture.
Clay Content Test: Clay content in sand is determined by washing the clay from a 50 g of sand in water and sodium hydroxide several times. After washing sand is dried and weighed. The decrease in weight is clay content in the sand.
Fineness Test: According to American Foundrymen’s Society Sieve Analysis, the foundry sand for its grain size is tested with the help of sieve. The test is performed on 50 g clay-free, dried sand sample. The sample is placed on the top of a series of 11 sieves having the numbers as 6, 12, 20, 30, 40, 50, 70, 100, and the sieves are shaken. The amount of sands retained on each sieve and the bottom pan is weighed and its percentage in total sample is determined. To obtain the AFS fineness number, each percentage is multiplied by a factor, which is the size of the preceding sieve. The fineness number is obtained by adding all the resulting products and dividing the total by the percentage of sand retained in the sieve set and pan.
Permeability Test: Permeability is a measure of gas passes through the narrow voids between the sand grains. It is measured in terms of a number known as permeability number. Permeability number is defined as the volume of air in cubic centimetres that will pass per minute under a pressure of 10 g/cm2 through a sand specimen, which is 1 cm2 in cross-section and 1 cm deep.
Permeability number,
where V = Volume of air, H = Height of specimen, P = Air pressure, A = Cross-sectional area of sand specimen, T = Time in seconds)
Compression Test: Compressive strength of moulding sand is found by this test. A compressive load of sufficient amount is applied on a cylindrical sample of 50 mm height and 50 mm in diameter so that it just starts to break. Sands of low moisture and excess moisture are said to have poor strength.
Hardness Test: Hardness test of sand mould or core is done on a hardness testing machine. It carries a hemispherical ball or tip at its bottom, which is penetrated into the mould surface. A spring-loaded shaft inside the hollow body of the instrument actuates the needle of the dial gauge fitted at the top. The dial of this gauge provides direct reading of the mould hardness.
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