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The forthcoming assessment is critically based on the types of molding sand and its properties.
Molding sands are usually compressed or heated as well as moistened by engineers to induce a specific shape.
The sand also termed as Foundry Sand as it is used in the casting process.
The sand casting process is generally used by manufacturers to develop a cavity in the mold. Most of the time silica sand is utilized by manufacturers in the casting process.
The sand casting process is formulated for casting non-ferrous and ferrous metal.
One of the most significant characteristics of molding sand is that it does not react any sort of time with the metal.
Hence this assessment precisely included the major types of molding sands along with their properties.
Types of Moulding Sand:
In the metallurgy enormous molding sands are present that are as follows:
- Green Sand
- Dry Sand
- Loam Sand
- Parting Sand
- Facing Sand
- System Sand
- Floor Sand
- Core Sand
- Molasses Sand
Let’s study one by one,
The green sand is tempered sand and contains enough amount of moisture.
Greensand contains a mixture of 15% to 20% of clay, 6% to 8% of water and silica. Strength depends on the mixture of water and clay. The mixture acts as the bonding material in the sand.
Greensand mold is that mold which is basically made from Green Sand. Greensand is soft, porous, fine and light in nature. It is used in rough and simple casting and both for non-ferrous and ferrous metals.
This sand feels damp when it is pressed in it.
The availability of green sand is good and it also costs low. So, green sand is commonly used by manufacturers most of the time.
Dry sand is the type of green sand, from which moisture is being removed.
Dry sand is made by baking or drying the mold made from the green sand in a decent oven. The dry sand contains a mixture of 15% to 20% of clay and silica.
This sand has more rigidity, thermal stability, and strength.
The casting of the dry sand is heavy and large. A dry sand mold is that mold that is made from Dry Sand.
Loam sand is like a thin paste of plastic in nature.
Loam sand is made up of the mixture of 30%-35% of clay, 18% of water and the rest of the thing is sand. With the help of Sweeping, shape is given to the loam sand.
In this sand, an appropriate amount of water is a must needed thing.
Loam sand mold is made from the loam sand. These molds from loam sand are heavy and large to be used in the hoppers and the parts of turbines.
Parting sand is the dry sand without a binder to induce a non-stickiness pattern. Parting sand is made of pure silica. Parting sand is used to make the parting mold.
In general cases, the patter is removed from the mold. Then the mold used to stick. So, parting sand is used as the mold does not stick.
Before attaching the mold with the pattern, such parting sand is used to sprinkle on the mold as after removing the pattern the mold does not stick.
In the drag, cope surface and cheek, parting sand is used as a sprinkle to avoid sticking.
Facing sand is that kind of sand that forms the face of the mold.
This sand is mainly used by manufacturers to form the face, the molten metal which is then poured thus, it is termed as the Facing Sand. Facing sand is consists of 5% of sea-coal and 25% of iron.
It is placed as the next surface of the patter to come in contact with the hot molten metal.
Facing sand has high refractoriness and very high strength. Facing sand is very fine in nature.
System sand is that sand that is used to fill the flask of machine molding.
As this sand is used in machine molding, it is termed as the System sand.
This sand has very high strength, refractoriness, and permeability. Along which that System sand has mechanical heavy casting.
In the machine molding, facing sand is not used as facing sand as it cannot be cleaned easily and apart from that system and it has some other special additives.
The floor sand is black in color. The facing sand is mainly backed up by the floor sand, for this reason, Floor sand is also known as Backing Sand.
The floor sand is used to fill the whole molding flask by backing up the face sand.
Floor sand is used by engineers, from very old times.
It is used as the alternative of the coal dust to face the hot molten metal.
Core sand is the sand that is generally used to make the core, for that reason, this sand is termed as Core Sand. Core sand consists of the mixture of core oils like resin, linseed oil, mineral oil, rich silica and the other binding materials like corn flour, dextrin, sodium silicate.
As the sand consists of oil, it is also named as Oil sand. It has remarkable strength which has great importance in the whole process.
At the time of use, water can be used in that sand to make the work easier.
Molasses sand is a small casting and core making sand which consists of molasses, for that reason, this sand is termed as Molasses Sand.
Properties of Moulding Sand:
Molding sand has many important properties. They are as follows:
- Green Strength
Let’s study one by one,
The property of Cohesiveness plays a very crucial role.
Cohesiveness is the property that can be termed as strength of sand.
Cohesiveness holds the other particles together, of the sand. It provides them with the strength to bear the molding process of the sand. Bentonite and clay help the sand to hold this cohesiveness property.
Insufficient strength might be the cause of the collapse.
Adhesiveness is the property that helps to lift properly of the cope along with sand.
For this property of Adhesiveness, at the sides of the molding box, especially in the inner wall the sand particles used to stick.
Porosity is the property that helps to pass the gasses and the steam of the molding sand. This property of Porosity is also known as Permeability.
The steam and the gasses got generated when the molten metal is poured into the cavity of the sand. These gasses and steam are used to hindrance the particles to give proper shape and size.
According to the binding material, moisture, amount of clay, this property depends. Along with that, the shape, particle size is also important to maintain this property.
The green strength is the property that comes out after mixing the water into the green sand. The water permits the mold to have enough toughness and strength at the time of handling or making the mold.
To make this property in action, there are some criteria also present. They are as follows:
- The grains of the sand must have the cohesiveness property as they can stick.
- Breaking of mold surface is not be taken.
- At the time of the flow of the molten metal, the wall of the mold erosion is should not be taken.
- Apart from that, the size and shape of the grain, moisture and amount of clay are also dependable.
Plasticity is a property that makes the sand compact in nature and flowed all around the corners of the mold like a fluid when the mold is rammed.
As this property flows like fluid all over the mold, so that, this property is also known as Flowability.
It used to flow uniformly when the mold is rammed. This property depends on the other property named as Green strength.
Plasticity and Green strength and those are inversely proportional to each other when the subject is about increasing the plasticity, then the green strength is decreased and vice versa.
Plasticity depends on the clay and the moisture in the sand.
Refractoriness is the property that is very important for molding sand.
By refractoriness, the mold does not break in very high temperatures as the molding process can be done with the help of high temperatures.
If this property of the sand becomes poor then the surface of the molding sand will not be so smooth after burning that.
This property depends on quartz content, SiO2 and the size and shape of the grain.
The sinter point of the sand is taken to measure the Refractoriness property rather than the melting point of the sand.
Concerning the above description of the Moulting sand, types of it and the properties of the molding sand are precisely included in this assessment. Therefore, it can be asserted that the field of metallurgy cannot be completed without the Moulding sand.
As we can see that Moulding sands are usually used to induce a specific shape by the engineers, hence a mold is needed to heat. For devising a proper shape and cavity to the mold there are so many properties that have vital roles. Along with that, there are so many types of sands and those have their different roles.
The above description is very brief that occupies the types and the properties of the Moulding sand. Lastly, it can be concluded that if an engineer wants to seek knowledge about Moulding Sand, this assessment can be a fruitful one.
Here is a Cool Video on Molding Sands:
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References (External Links):
- Casting Process – an overview
- Metal Casting at Home [Youtube]
- Mechanical Engineering – Metal Casting – NPTEL
- Video By: MP Dragon
- Feature Image: Modified by Author