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Posted on Aug 26, 2020
Casting is broadly defined as the process of forming a substance into a specific shape using a mold. Metal casting uses a variety of metals to create a molded end product and goes back thousands of years.
During the iron casting process, the manufacturer deposits molten iron and iron alloys into a mold. This material solidifies as it cools, eventually hardening to the shape defined by the mold cavity. The casting process promotes important microstructural changes in castings.
:: Read more : Introduction to Cast Iron Castings
Casting today creates many products of great commercial importance. The three popular different castings often contribute to the production and assembly of metal parts. These include gray, ductile and malleable cast iron.
• Gray iron : Gray iron castings, known for their distinctive gray color, have found widespread use in many modern industrial applications.
• Ductile Iron : Manufacturers make ductile iron by depositing magnesium over iron metals used in the production of gray cast iron. Ductile iron castings show in ductile iron carbon inclusions at the granular level, which contributes to increased ductility.
• Malleable Cast Iron : This cast iron product contains less carbon than conventional gray cast iron. Provides plasticity and strength, but sometimes shrinks when cooled.
:: Read more : How to choose the right grade of Ductile Cast Iron
Manufacturers produce malleable cast iron by first casting a brittle product known as "white iron". White cast iron contains carbon inclusions and provides surface hardness. The use of special annealing heat treatment causes the metal to lose its brittleness, while changing the internal microstructure to make it more flexible.
Manufacturers must be careful during the annealing process to prevent the Ductile iron castingsre-formation of brittle iron.
This step sometimes involves reheating thin sections of cast material to ensure that the carbon inclusions form irregularly shaped structures referred to as “temper graphite nodules” or “temper carbon nodules” on a microstructural level. The high temperatures reportedly approach 1,700 degrees Fahrenheit during prolonged reheating operations.
In some cases, manufacturers will reheat white iron for longer periods (up to 100 hours) during the production of malleable iron. At this stage, they can add extra iron ore to the molten metal.
Since companies with both "low tech" and "high tech" foundries produce malleable cast iron, there are clearly differences in production methods in today's commercial market.
Malleable cast iron is more ductile than gray cast iron and, although hard, lacks the brittleness of white iron. While not as easily cast as gray or ductile iron, it will be cast better than some other materials, including white iron.
In addition, malleable cast iron provides excellent surface hardening. It is resistant to scratches and abrasions. It has better tensile strength compared to gray iron, although far less tensile strength than ductile iron.
Its ductility means that malleable cast iron allows a variety of "cold work" operations during the finishing process. Its increased ductility makes the malleable cast iron well suited to machining. We can bend, straighten or stamp this metal to create salable items. Malleable cast iron will tolerate these operations.
One property of malleable iron is a disadvantage of its use in some commercial applications. Sometimes it contracts when cooled. The loss of dimensional stability makes it unsuitable for the manufacture of products requiring high tolerance ranges.
However, many manufacturers use malleable cast iron to make small thin castings and plates.
:: Read more : The Many Advantages of Gray Cast Iron
Malleable cast iron has been around for centuries. Some of the products using this cast metal date back to ancient times.
For example, an archaeological excavation has reportedly discovered malleable cast iron artifacts dating back to the Tang Dynasty.However, its use became widespread only after the Industrial Revolution.
Today, manufacturers can still use malleable cast iron in a variety of products where the production of large numbers of uniform parts within tight tolerances is not an overriding problem.
It often creates small parts for extensive subsequent machining and finishing operations.
Malleable iron applications today exist in many industrial sectors, including agriculture, electronics, consumer goods and construction.
Malleable iron products include:
• fencing equipment
• pipe fittings
• agricultural equipment
• household items
• small machine parts
• costume jewelry
• electrical equipment
• stamped industrial labels
works of art, etc.
This material works well for creating very thin castings and plates.
Malleable cast iron has several advantages.
Provides greater ductility than many alternative casting materials, making it an excellent choice for products that will undergo extensive treatment during finishing. Although it lacks the flexibility, tensile strength and impact resistance of ductile iron, it allows extensive handling during processing without cracking.
Malleable cast iron will allow manufacturers to flatten them and hammer them during finishing. In such a situation, some competing forms of cast iron would crack. This metal provides an excellent surface for stamping and deburring operations.
The strength of malleable cast iron allows it to compete with both gray and nodular cast iron for some purposes. It has gained wide application in the metal parts manufacturing industry.
Some malleable cast iron grades have gained utility due to good impact resistance at very low temperatures. Tags made of this metal can withstand harsh arctic conditions, for example.
Some metal casting processes and materials used in antiquity are still in use today. There are many reliable and effective casting materials that are used for industrial purposes. The most commonly used resources are:
• gray iron
• Tough metal
Gray cast iron is one of the most widely used casting materials in industrial production. With a high proportion of die casting supply markets, it is a powerful all-rounder. Gray cast iron is easy to machine, quality tested without destructive methods, formulated to meet specific application requirements and is cost effective for large volumes. It is suitable for a variety of applications including those that require:
• Vibration damping or control
• High strength-to-weight ratio
• Dimensional stability
• casting iron in a foundry
• Ductile iron casting
For processes requiring greater strength than that provided by gray iron casting, ductile iron casting may be a useful alternative. Ductile iron has similar characteristics to gray cast iron and therefore has many of the same advantages. However, ductile iron differs from gray iron casting as follows:
• Greater strength
• Improved wear resistance
• Stronger endurance
• Perfect plasticity
• Weight reduced
• Reduced shrinkage
• Lower cost
• Die-cast aluminum
Aluminum is also a widely used foundry metal, in large part because of its exceptional versatility. As one of the few materials that can be subjected to most metal casting processes, aluminum is a substance relatively adaptable to work. The corrosion resistance of aluminum, high thermal / electrical conductivity, good mechanical properties and high temperature strength make it an effective choice for:
• Permanent mold casting
• Investment casting
• Sand casting
• Lost foam casting
• Squeeze the casting
• Hot isotonic pressing
Steel is a heavy-duty casting material that is well suited to producing parts that will be exposed to extreme wear, impact or heavy loads. It is useful for resistance to corrosion in an aqueous environment and in applications involving elevated temperatures. Steel is often mixed with chrome, iron and nickel to further improve its corrosion or heat resistance.
The main advantage of copper as a casting material is that it provides excellent electrical conductivity. As a result, the construction industry often uses copper to produce electrical components. Other benefits of copper include:
• Good plasticity
• Perfect plasticity
• Good heat conduction
However, copper and castings can be subject to surface cracks, porosity, and internal cavity formation. Consequently, it is often mixed with other metals (silicon, nickel, zinc, chromium, tin and silver) to alleviate these problems.
Zinc's low melting point (425 degrees Celsius) makes it a suitable material for die casting applications. It is relatively easy to cast alloy due to its fast filling and rapid cooling. In terms of cost, zinc can be an economical option for casting small parts with a large volume.
Casting is used in many manufacturing processes and plays an important role in construction. The creation of uniform products in many industries is highly dependent on castings.
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