In this article, we shall explore the types of molding sand and their properties. We have provided a PDF download for the same.
Molding sands are usually compressed or heated as well as moistened by engineers to induce a specific shape. The sand is also termed 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 for any sort of time with the metal.
Types of Moulding Sand
In the metallurgy enormous molding sands are present in various forms as follows
- Green Sand
- Dry Sand
- Loam Sand
- Parting Sand
- Facing Sand
- System Sand
- Floor Sand
- Core Sand
- Molasses Sand
Green Sand
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 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
Dry sand is the type of green sand, from which moisture is removed. Dry sand is made by baking or drying the mold made from 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
Loam sand is like a thin paste of plastic in nature. Loam sand is made up of a mixture of 30%-35% of clay, 18% of water and the rest of the thing is sand. With the help of Sweeping, the 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 loam sand. These molds from loam sand are heavy and large to be used in the hoppers and the parts of turbines.
Parting Sand
Parting sand is 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 pattern is removed from the mold. 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
Facing sand is the 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 the Facing Sand. Facing sand 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
System sand is the sand that is used to fill the flask of machine molding. As this sand is used in machine molding, it is termed the System sand. This sand has very high strength, refractoriness, and permeability. Along with that System sand has mechanical heavy casting. In 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.
Floor Sand
The floor sand is black. 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 an alternative to coal dust to face the hot molten metal.
Core Sand
Core sand is the sand that is generally used to make the core. Core sand consists of a mixture of core oils like resin, linseed oil, mineral oil, rich silica, and other binding materials like corn flour, dextrin, and sodium silicate. As the sand consists of oil, it is also named 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
Molasses sand is a small casting and core-making sand which consists of molasses, for that reason, this sand is termed Molasses Sand.
Properties of Moulding Sand
Molding sand has many important properties which are as follows
- Cohesiveness
- Adhesiveness
- Porosity
- Green Strength
- Plasticity
- Refractoriness
Cohesiveness
The property of Cohesiveness plays a very crucial role. It is the property that can be termed as the 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
Adhesiveness is the property that helps to lift properly the cope 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
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 hinder the particles to give proper shape and size. According to the binding material, moisture, and amount of clay, this property depends. Along with that, the shape, and particle size are also important to maintain this property.
Green Strength
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
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, 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 Green strength.
Plasticity and Green strength 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
Refractoriness is the property that is very important for molding sand. By refractoriness, the mold does not break at 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.
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.
Cast Aluminum Process Using Sand Mold
Here is a Video on Molding Sands
FAQ
What are the various applications of sand casting
Sand casting or Molding sand has a multitude of applications across various industries. It is widely employed for shaping and fabricating metal parts with complex structures. Common uses include automotive components like engine blocks and cylinder heads, as well as aerospace parts, agricultural machinery, and industrial equipment.
Additionally, sand casting enables the creation of artistic sculptures, decorative items, and architectural elements. This versatile and cost-effective method accommodates both small and large-scale productions, making it highly valuable in diverse manufacturing contexts.
What are the advantages of sand casting or Molding sand
Sand casting, or molding sand, offers numerous advantages in the manufacturing industry. It is a cost-effective method due to the abundance and affordability of sand. The process enables the creation of intricate and complex shapes, making it versatile for various applications.
Sand casting provides high dimensional accuracy and excellent surface finish, ensuring top-notch quality. It is suitable for both small and large-scale production. Furthermore, sand casting is flexible and can be used with a wide range of metals, including ferrous and non-ferrous alloys. It is a relatively simple and adaptable process, suitable for different manufacturing settings, regardless of technological sophistication.
Conclusion
In conclusion, molding sand plays a crucial role in the casting process, and understanding the types and properties of molding sand is essential for achieving high-quality castings. The four main types of molding sand green sand, dry sand, chemically bonded sand, and ceramic sand – each has unique properties that make them suitable for different casting applications.
These properties include permeability, compressive strength, collapsibility, and thermal stability. By selecting the appropriate molding sand type and optimizing its properties, foundries can improve casting quality and efficiency while reducing costs.
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