Forging is the process of forming and shaping metals into desired shapes that provides various advantages over other manufacturing operations.
The advantages of forging include better mechanical strength, high tensile and shear strength along with higher fatigue strength and creep resistance. Forged parts have a uniform grain structure leading to enhanced mechanical properties and high reliability with a lower production cost than other metalworking operations.
This article discusses the advantages of forging in detail and provides a detailed comparison of forging against casting and machining.
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Advantages of Forging Explained
Forging is a metal-forming process in which the workpiece is shaped into the desired form by applying pressure, which makes it comparatively easy than other metalworking operations like casting and machining.
Depending upon your application, you can select the best-suited type of forging for your application.
Apart from that, the parts produced by forging provide various advantages over parts produced by other operations.
High Strength of Forged Parts
The strength of the forged parts is far superior to cast or machined parts.
Forged parts have a smaller grain size, and the grain flow aligns with the part's shape. This results in better tensile and shear strength, and the parts have consistent mechanical properties.
Forged components have better fatigue strength and do not deform under long-term exposure to high stresses, known as creep resistance.
The grain flow is controlled to achieve better directional strength along the direction of stresses, leading to improved ductility, while enhancing their ability to withstand fatigue and impact loads.
Apart from that, forging also eliminates any internal voids or gas pockets present in the metal.
This enhances its strength and provides a uniform structure that is suitable for heat treatments like annealing, normalizing, tempering, etc. and machining operations.
These enhanced mechanical properties make forging best suited for applications where high strength and reliability are required.
Low Production Cost
Although forging equipment is generally more costly than metal melting tools required for casting, its low production cost makes it suitable for large-scale production units.
Using die forging eliminates the need for any skilled operator, reducing the cost of manpower. Furthermore, the process can be easily automated, which further reduces operational costs.
Closed die forging also leads to material saving by minimizing flash formation. It also eliminates or minimizes the need for secondary machining operations, which reduces production time and cost.
Apart from that, the increased strength of forged components enables to use elements with smaller cross-sections without the risk of failure, reducing material costs.
The forged parts also have a longer usable lifespan due to better mechanical properties. All these factors contribute towards bringing down the overall costs incurred during the product lifecycle.
High Reliability of Forged Parts
The structural reliability of forged parts is superior to other metalworking processes like casting, making it an ideal operation for parts where reliability and safety are essential.
Forged parts are free from defects such as voids or gas pockets, preventing unforeseen or sudden failures under loads.
However, there are other forging defects that you need to be wary of to ensure the high reliability of the workpiece.
The forging process also homogenizes the chemical composition of stock by displacing the material in all directions, improving reliability.
This uniformity of mechanical properties throughout the workpiece provides the ability to predict the forged component's response toward various stresses, eliminating the risk of unexpected failures and enhancing reliability.
Generally, drop forging is best suited to produce parts with high strength and reliability.
Versatility
Forging is a very versatile process, and you can use it to make various products ranging from simple shapes such as rings, shafts, bars, etc., to parts having complex shapes.
The versatility of forging allows you to make specialized single-body components, making the part more robust.
As a result, forged components are commonly used for manufacturing simple hand tools and other complex equipment for various industries such as aerospace, automobile, and railroad industries.
Material Flexibility
Different metals have unique characteristics, making them suited for various applications. You can use forging operations to shape most metals in the required form.
With some process variations based on the metal used, forging can work with hard or soft metals, including various alloys.
Some of the commonly used materials include alloy steel, carbon steel, micro-alloy steel, stainless steel, and non-ferrous/non-magnetic metals including aluminum, brass, copper, and titanium.
How does Forging Compare to Casting and Machining?
| Parameter | Forging | Casting | Machining |
|---|---|---|---|
| Strength | Highest strength | Lower strength | Susceptible to cracking |
| Internal Structure | Uniform structure | Granular structure | Discontinuous along the machined area |
| Complexity | Ideal for parts with simple geometry | Ideal for parts with complex geometry | Ideal for parts with almost any geometry |
| Finishing | Minimal finishing required | Secondary finishing is always required | Finished products can be made |
| Cost | Minimal production cost | Average production cost | High production cost |
| Material | Optimum material utilization | Minimal material wastage | High material wastage |
Comparison Based on Strength
The strength and structural integrity of forged parts are the highest for the same material and design, mainly due to grain conformance.
Although casting shows good resistance to compressive loads, it cannot withstand high shear and tensile loads.
On the other hand, machining a component results in material removal, reducing the number of grains along the cross-section, and rendering the workpiece prone to cracking along the machined area.
Therefore, when comparing forging against machining and casting, forging produces parts with greater strength, making it suitable for load bearing applications.
Comparison Based on the Uniformity
Forged parts have uniform properties throughout the cross-section, making them highly reliable.
On the other hand, cast products have a porous structure with various internal defects such as inclusions, air gaps, etc., which lead to less uniformity in their mechanical properties.
Machined components are uniform in their dimensional tolerances, but mechanical properties may vary to a certain extent.
This is because the grain structure is discontinuous along the machined area, which reduces its strength and other mechanical properties.
Comparison Based on the Design Ability
The forging process can produce various shapes but is limited by the level of complexity the parts can have.
In contrast, cast or machined products can be made in almost all shapes and sizes with high tolerances.
However, casting can be limited by the complexity of the mold and the ability to retrieve the complex part from the mold, whereas, machining provides the ability to manufacture almost any complex shape with high tolerance.
Comparison Based on the Surface Finish
Precision forging can produce parts that require no finishing operations, but common forging operations require secondary finishing.
Cast products always require finishing operations due to the presence of gates, risers, and runners, which need to be removed.
On the other hand, machined components can be finished during the production process itself.
Comparison Based on the Cost
The cost involved in these processes can be divided into initial costs and operational costs.
While forging requires the highest initial investment to get heavy-duty machinery, casting and machining equipment are comparatively cheaper.
However, the production cost of forging is much lower than casting and forging, making it ideal for large-scale applications where the high initial investment is compensated by low manufacturing costs.
Apart from that, forging also reduces operational costs by minimizing wastage and significantly lowering the cycle time.
On the other hand, machining and casting require a long cycle time and involve material wastage in the form of machined chips and unwanted projections in casting.
Comparison Based on the Material Utilization
Forging, casting, and machining are the three basic metal processing techniques that can be applicable to almost any metal, provided you use the right metal melting tools, hammers, and cutting tools.
However, forging provides the maximum utilization of the metal by minimizing the generation of scrap during the process.
Whereas, the runners and gates result in unwanted projections in casting, which are later machined and removed.
On the other hand, machining is a subtractive manufacturing process and leads to a lot of material wastage in the form of chips.
Final Thoughts
Forging results in high-strength components with superior mechanical properties and lower production costs than other processes.
The parts are highly reliable, and the process is suitable to produce a wide range of products from different types of metals and alloys.
However, it involves a high initial investment and is limited in terms of the complexity of the part to be produced.
As a result, forging is generally preferable for large-scale manufacturing of parts with simple geometry.
If your part demands high strength and reliability, it is always advised to opt for forged parts over casting or machined parts.
Frequently Asked Questions (FAQ)
What are forging defects?
Several forging defects could arise due to improper process control. The common forging defects are unfilled die sections, cold shut, scale pits, die shifts, flakes, and improper grain flow. These defects can be minimized by controlling the process parameters such as temperature, stock size, etc.
What is cold shut in forging?
Cold shut is a common forging defect at the intersection of horizontal and vertical components. This is also known as lap or fold, as the metal folds over itself and appears as a crack or lump, impacting the component's strength. This defect can be minimized by controlling the stock size and the forging temperature.
What is segregation in forging?
Segregation in forging is the lack of homogeneity in the chemical composition in different areas of the forged product. During the solidification process, the alloying elements are not uniformly distributed over the entire part due to the slow release of heat. This leads to non-uniform chemical and mechanical properties.
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