In this article we will learn about properties of sand which are desirable in moulding process. Before we start this article, we need to understand the basic concept that a moulding is done at a very high temperature. So the basic is that the moulding material should have high refractoriness. There are many metallic and non metallic material can use to mold manufacturing but sand is the mostly usable non metallic material for moulding. It has high refractories properties and has high chemical stability at high temperature. It is easily available, cheap and can be shaped easily.
One question arises in your mind that the refractory is the only property that’s why sand is choosen. The answer is NO.
There are many other basic properties of sand due to which it is using in moulding. These are given below
The basic and main sand properties for moulding are given below.
It is the basic and most desirable properties of moulding material. It is define as the property of a material to withstand with high temperature without any crack or braking of mold, which can provide good casting. This property of sand can be extending to some extent by mixing some adhesive. The poor refectories give poor surface finish and poor casting. The degree of refractoriness depend on the SiO2 contain and grain size of the sand. The higher the SiO2 contain give higher refractoriness.
It is the property which allow to escape any gas, air and moisture content from the mold. It is called porosity or permeability. This property is desirable for making cast without any defect. All of these gases and air particles generated during pouring and solidification of molten metal into the mold. These particles should removed from the mold before casting, otherwise it will generate many defects in the casting product and decrease its strength. Permeability is function of grain size, moisture and clay contain.
Cohesiveness is the property due to which the sand particle attracts each other within the mold. It is the property which increases the binding capacity of moulding sand which make good mold.
The strength of sand mold mixed with water generally called green strength. The sand mixed with water should have sufficient strength and toughness to handle the mold. Green strength of sand is mostly depends on the adhesive and cohesive property of sand. Adhesive is property by virtue of which the sand particles attract other particles which makes strong bond between sand, clay and moisture particle. It is desirable for strong mold. The cohesiveness of particle is desirable to taking out the pattern from the mold without breaking it. The green strength is depends the grain size, clay contain and moisture contain in the sand.
When the molten metal gets contact with the mold, the moisture of adjacent layer evaporates which makes it dry. So the dry strength of sand should be sufficient enough so it can be withstand with molten metal. Flow ability and plasticity It is the ability of sand which allows it to flow like fluid into the mold. This property of sand is required to make uniform mold. It allows the sand particle to flow all over the mold during ramming process and also increases with decreasing in green strength. It is also depends on the grain size, clay and moisture content.
It is the property of sand due to which sand particles attract other particles. It is desirable for the making strong mold.
Collapsibility is a property of sand which is behind to avoid cracks in casting after solidification. After the molten metal get solidified into the mold, the mold should be collapsible which allow free contraction of metal which avoid tearing and cracking of casting product.
These all are desirable properties of sand which allow the sand to use in moulding process. It you have any doubt about this article, ask by commenting. If you like this post, don’t forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.