In the manufacturing industry, the casting metal process is among those processes which have an extensive history. Humankind is using this process since ancient times, and it makes them equipped with some of the essential things.
Gradually it became an integral part of metalworking. Nowadays, people are using it for making all sorts of apparatus and different components.
Let’s learn the basics of the casting process with its benefits, limitations, types, and some of the fundamental defects.
Let’s try to understand casting metal basics. It is simply the process in which setting of molten metallic material takes place in a pre-designed mould.
Casting is the process that can be achieved with numerous metals and different materials that are used for constructing the moulds as well as different equipment.
The following precautionary measures shall be taken care of, as follows:
Basic terminologies or gradual steps in the casting process helps to understand the core of the process. This is important to get a comprehensive and holistic view of the casting process.
This is the foremost step that is a crucial one in the whole casting process. Pattern development or pattern making is the process of constructing the pattern as per the needs.
Mould preparation or mould making is an essential process in which a specific material is used for preparing the mould of the original model.
This process holds the primary material and the whole melting process of the metal. It is one the foremost step without which the casting cannot be attained.
Metal pouring is the technique through which molten metal is introduced into the moulds.
After the metal pouring process, the molten metal keeps on for a cooling period.
After the cooling process in casting now, the next process is to part removal. Part removal is nothing but the process in which different parts of moulds are cleaned.
Specifically, this process involves some of the critical methods that help in part removal such as shakeout in which a vibrating device is used for shaking and casting out the flask from the mould.
This is one of the simple processes that includes removing those materials which are in excess. These include risers, rough edges, impurities etc.
Heat treatment is a vivid process, but when it comes to casting, then this process is used for controlled cooling and heating that helps in attaining different properties of metals after crystallization.
There is a different consideration that comes when we design the material. In casting this method is an alternative step that may or may not is used.
If there is something specific we need, then this upgrade treatment is used.
Sometimes casting provides those end products that are equipped with rough edges or abnormal risers.
To repair those one uses different finalization processes in which one of the best ones is machining.
The working of the casting metal process can be expressed, as follows:
Casting metal is a process that holds massive importance against different shaping processes such as,
The primary advantages that provide an upper hand to casting over other methods are as follows:
Apart from the compelling advantages, there are some of the disadvantages of this process, but these are way minimal in comparison to the benefits. Some of them are as follows:
Numerous types of casting can be categorized based on essential parts in which one of the prominent ones is moulds. The different kinds of casting can be further elaborated based on moulds permanence attribute. The two types of casting techniques based on moulds are as follows:
Expendable casting is the kind of casting technique that mainly uses clay, plastic, metal moulds and sand for the casting process. These moulds are only for one-time use and discarded after use.
Non-expendable casting is the type of casting in which the moulds can be used for long runs. In a way, these moulds are for permanent usage. Mostly these moulds are made up of metal through the whole process of performing the casting is different from the expendable methods. These two casting types are the core types of methods. There are further subdivisions in each one of them which are categorized based on the use of material to construct the moulds.
Expendable mould casting is further subdivided into three categories of casting processes. The following are the further elaboration of the same:
Sand casting is a process in which the moulds are manufactured with chemicals and polymers. These moulds are of par level durability and can be used for other expendable casting methods. It can be used for long runs.
This process mainly depends upon silica-based materials such as naturally bonded or synthetic sand. The casting sand has some of the properties that make it quite apt for this process, such as spherical grains, finely ground.
It helps in attaining a tight packing-which is capable of providing a smooth moulding surface.
Reasons for using this method
This casting technique helps explicitly in reducing the probability of cracking, tearing and other defects by providing a moderate level of shrinkage and flexibility in the cooling phase of the whole process. The addition of clay helps the particles to be bonded effectively. One of the popular uses of this technique is in casting automotive products such as engine blocks.
Steps involved in sand casting
There are several steps involved in sand casting. The following are some of them:
Advantages of sand casting
Disadvantages of sand casting
Plaster mould casting is the method of casting that is comparatively less durable than sand moulding. This consists explicitly of gypsum plaster. In this process, the time required to manufacture the mould is minimal.
Reason for using this method:
Where there is a need for an optimal surface finish of the yielding material, this method is used.
Steps involved in plaster mould casting:
The essential steps in plaster mould casting are somehow similar to sand casting. However, in place of sand, it uses a mixture of gypsum, strengthening compound and water.
Advantages of plaster mould casting
Disadvantages of plaster mould casting
Investment or lost wax casting is a process that is a technologically advanced method of casting that is suitable for getting durable and stable shapes. It is used for casting different shapes from massive to tiny pieces. It is the casting type that is suitable for complex geometries and alloys.
Reasons for using this method
This method is used where there is a need for casting complicated geometrical shapes. Mostly this method is used for the aerospace, power generation and automotive industries where there is a critical need for parts with complex shapes such as,
Steps involved in investment casting
Advantages of investment casting
Disadvantages of investment casting
Below mentioned are some of the subdivisions of non-expendable mould casting:
It is a casting method in which a die is formed that provides a horizontal pattern. This is the method that helps in moulding materials with the help of high pressure.
It is useful for non-ferrous metals and alloys such as copper, aluminium, zinc and tin.
The process of casting involves pattern preparation, injection of molten metal into the die with high pressure. The high pressure continues until the yield gets solidified. The pressurized insertion helps in preventing the sections of material from getting hardened before being cast.
Once the process gets completed, the yield is removed, and all the scrap material is removed.
Advantages of Die-Casting
Disadvantages of Die-Casting
This is a non-expendable casting process in which metal moulds are used. These metal moulds can be used for long runs. However, the nature of mould is semi-permanent. This process shares a similarity between centrifugal and die-casting.
The moulds in this method can be made up of graphite, steel etc. this casting method is used to cast materials such as magnesium alloys, lead, aluminium, zinc, cast iron, and certain bronze.
Advantages of Permanent Mould Casting
Disadvantages of permanent mould casting
Centrifugal casting is a type of non-expendable casting method that includes a large drum creating a centrifugal force by turning. It helps in pushing a molten metal into a mould that precisely fills out as per the design.
This method of casting helps produce intricate shapes and smaller pieces. One of the best uses of this casting technique is in the jewellery industry.
Advantages of centrifugal casting
Disadvantages of centrifugal casting
The role of gas, mould, pouring of molten metal and metallurgical properties are foremost in this process. The significant defects that occur in the metal casting process come due to excess or shortage of the same.
Like welding defects, below mentioned are the common defects that affect the efficiency of this process,
Gas defects mainly include Blowholes and open blows, Air inclusions, Pinhole porosity, Shrinkage cavities.
Mould is among the foremost process that comes into play at every consecutive stage. Different kinds of defects persist due to the mould such as,
Pouring of molten metal can be a cumbersome process. This complexity results in different kinds of defects such as,
Metals have different properties, and when the other thermodynamic processes are used, then it may cause metallurgical defects as well. Some of these defects are,
There are many other castings defects, incurred in various metals, as follows:
In this excerpt, we have studied one of the oldest known manufacturing processes that have it’s own advanced and modern version. With the advancement in technology, we have utilized the same with this process also.
Apart from the core process here, we have emphasized different aspects of the casting techniques, it’s advantages and disadvantages with the possible known defects. However, there is a massive possibility to gain further insights into this process.
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