Difference Between Forging and Casting: With Process and Types

Forging & Casting are two popular methods of working with metal for manufacturing purposes. Both processes differ in their work techniques, benefits, and disadvantages, thus making them appropriate for different applications. This article seeks to help manufacturers and engineers make better decisions.

What is Forging?

Forging is considered a process of manufacturing that involves deforming metal through the application of compressive loads. In most instances, the metal is heated so it can be worked to the desired shape either by hammering or pressing. Forged parts are known to be stronger and more durable than cast parts which makes them useful for demanding applications. Thus, forging is common in aerospace, automotive industries, and machinery.

Types of Forging

Various types of forging exist, some of which cater for different needs. Following are examples of different types of forging;

• Open Die Forging: In this method the metal is placed between two flat dies and hammered to shape the part so that it produces large and simple parts.

• Closed Die Forging: The metal is placed in a die with cavity and under pressure, the metal fills the cavity. This method is great for complex shapes or parts that require high accuracy.

• Rolled Ring Forging: In this method, a ring of metal is rolled between two dies. It is most useful for making big rings, such as those fabricated for turbines.

• Rotary Forging: The workpiece is rotated under a forging machine while being pressed to produce tubular or cylindrical shapes.

Read also: Sheet Metal Fabrication Techniques

Forging Process  

The steps involved in forging are:  

• Heating: The metal part is brought to a certain temperature to increase its malleability.  

• Shaping: It is then treated with either a hammer or a press to mold it into a specific design.  

• Cooling: In most instances, forged components are cooled in air or water with the intention of enhancing its properties.  

• Finishing: Further machining, grinding or coating may be done to the forged components to achieve the desired final specifications.

Advantages of Forging  

There are some advantages of forging.

• Strength and Durability: Forged components have distinct advantages in mechanical properties such as high resistance to wear, fatigue, and impact.  

• Uniformity: The forging process allows for molding the grain structure of the metal, enabling uniform distribution of strength throughout the part.  

• High precision:  Closed die forging yields highly precise components, which is ideal for more stringent applications.  

  
  

Disadvantages of Forging  

• Cost: The use of high temperatures, specialized equipment, and complex shapes to be forged results into an expensive process.

• Material Waste: Certain forging processes creates waste, particularly when a significant amount of metal is cut away to achieve the desired outline.

• Limited Design Flexibility: There are fewer types of shapes in forged products relative to those made through casting methods. 

  
  

What is Casting?

The process where a liquid metal is poured into a mold and allowed to harden to take the shape of the mold is known as casting. It is one of the oldest techniques of manufacturing, widely used for making intricate components that are difficult or costly to forge. Metals that can be used include aluminum, bronze, cast iron and steel.  

Types of Casting Methods 

There are several casting methods, each tailored to meet varied needs.  

• Sand Casting: This is done by pouring the metals into a mold made of sand. This method is economical and flexible, but it is often less precise.  

• Die Casting: This is a high pressure method that forces molten metal into a steel mold. This method is perfect for middle range sizing and bulk production.  

• Investment Casting: This is complex because it uses a wax pattern covered in a ceramic shell which is melted later, leaving a detailed design. It's ideal for complex parts.

• Permanent Mold Casting: Molten metal is poured into a mold, usually made of metal and is further used for stronger parts with high precision.

• Shell Mold Casting: High precision components are fabricated using machined, detailed shapes with a metal shell mold for added exit detail.

  
  

Casting Process

The following methods are used in casting:

• Mold Creation: A mold is prepared, using sand, metal, or ceramic based on the casting type.

• Melting the Metal: The metal is put in a furnace and turned into liquid.

• Pouring: The liquid metal is poured into the mold to ensure all spaces are filled.

• Cooling: The liquid metal is cooled to form a solid and the cast takes the shape of the mold used.

• Finishing: The cut rough edges are smoothed out and the rough casting is separated from the mold.

  
  

Advantages of Casting

• Flexibility of Design: It is easy to create complex parts when using casting as compared to forgings.

• High Precision Components at Lower Cost: In the case of large parts or intricate ones, casting becomes less expensive than forging, particularly in low- to medium-volume production.

• Diverse Materials: It gives the advantage of using a greater range of metals to be used in casting, such as alloys or specialized materials.

  
  

Disadvantages of Casting 

• Lower Endurance: Due to internal casting defects, casted parts may not have internal strength characteristics on par with forged parts. 

• Additional Work Required: Surface treatments or machining are often required for cast parts to meet the desired accuracy and surface finish.

• Quality Assurance: The use of new molds and the changeable cooling rates can cause differences in later products. 

What Are the Key Differences between Forging and Casting? 

The differences between both forging and casting methods are summed in the table below: 

Aspect	Forging	Casting
Process	Metal is shaped by compressive force	Metal is poured into a mold to solidify
Material State	Typically hot or warm	Molten or liquid
Strength	High strength and durability	Generally lower strength compared to forging
Design Flexibility	Limited to simpler shapes	Highly flexible, can produce complex shapes
Applications	Automotive, aerospace, and industrial components	Engine blocks, machine parts, and decorative items
Cost	More expensive due to equipment and labor	Less expensive for complex shapes

Ideal Use Cases For Forging 

An ideal candidate of forged products is any for which strength, durability, dependability and reliability are crucial. Some of the most common uses include:

• Aerospace components: Parts that endure a lot of stress like turbine blades, landing gears, and fasteners.

• Automotive: Rotating shafts and connecting rods.

• Industrial equipment: Parts with heavy wear include pumps, valves, and gears. 

Examples of forged products

Some common forged products include: 

• Forged crankshafts.  

• Forged gears.  

• Forged axles and shafts.  

• Aircraft components.  

  
  

Ideal applications for casting

Casting is best for parts that have complex features, but less strength than forged parts. It is also used when a high volume of a single product is desired. Some commonly used cases: 

• Automotive: Engine blocks, cylinder heads, and transmission cases.  

• Aerospace: Engine parts such as brackets, housings, and supports.  

• Art and decoration: Fixtures of a sculptured, ornate nature and decorative features. 

Examples of cast products

Some examples of cast products are: 

• Engine blocks  

• Pipe fittings  

• Statues and sculptures  

• Machine housings  

Choosing the right process for your project 

When considering whether to forge or cast a part, the following should be kept in mind: 

• Strength requirements: If the part succumbs to high stresses, forging is a better choice.  

• Complexity of the design: More intricate shapes or patterns are better suited for casting.  

• Volume of production: For mass production, casting is sometimes the most economical option.  

• Material type: If dealing with particular alloys or specialty materials, casting may be more advantageous.

  
  

Conclusion

Both forging and casting have their specific advantages depending on a project’s requirements. Understanding the difference between the two will enable systemized manufacturers to devise strategies that yield better results during optimized production cycles.