Major Differences Between Casting and Forging: A Detailed Comparison

Casting and forging are probably two of the oldest manufacturing techniques known to humanity. These methods have been integral to human civilization since ancient times, with evidence of their use dating back to at least 4000 BC. Throughout history, casting and forging have involved in the development of tools, weapons, and artifacts that have shaped societal progress. From crafting simple agricultural implements to creating intricate ceremonial objects, these techniques laid the foundation for modern manufacturing processes and continue to be essential in today’s industrial landscape.

Casting and forging, what are the differences? Why are these two methods so popular, and how have they become so important in our daily lives? Today we will talk about these two useful techniques—their history, detailed processes, differences between casting vs forging, and most importantly, their applications. Last but not least, we will discuss how you should choose reliable manufacturers that can carry out these manufacturing processes to achieve your manufacturing projects.

casting vs forging

Understanding Casting

What is casting?

Casting, AKA metal casting, is a manufacturing process designed to create metal components using several different processes with various types of materials for different needs. It is involved in basically every aspect of our lives. For example, consider the car you drive; do you know how many metal components are required for a car to function properly?

A typical automobile contains thousands of metal parts, many of which are produced through casting processes. These components are crucial for the vehicle’s performances, safety and reliability. Components like engine blocks, cylinder heads, transmission housings, brake components and suspension parts are all made by casting methods. Another great example is the railway industry. Railway components such as rails, switching systems, couplings, brackets, and various fittings are often produced through casting. These components must withstand immense stress and environmental factors to ensure the safety and efficiency of rail transportation.

metal casting

If I were to list all the parts, I could go on for three days non-stop and still wouldn’t be able to cover 1% of the use cases. This shows just how integral casting is to modern manufacturing. Without castings, our lives would be drastically different; many of the conveniences and technologies we take for granted simply wouldn’t exist. From transportation and infrastructure to consumer goods and medical devices, casting plays an irreplaceable role in shaping the world around us. These examples showcase the importance of casting, and we will also cover the importance of forging, so we can closely compare casting and forging.

Types of Casting Methods

Before comparing the differences between casting and forging, lets first look at several casting methods, including Investment casting, sand casting, die casting and shell mold casting. These processes are used for achieving different desired outcomes, fulfilling different requirements. Now let’s about these casting processes.

Investment casting

Investment casting uses a wax pattern to create a ceramic mold. The wax pattern is coated with a refractory ceramic material. Once the ceramic shell is formed, the wax is melted out, leaving a hollow cavity into which molten metal is poured. Investment casting is great for parts that have intricate shapes, that require higher precision than other casting methods, a smoother surface. Investment casting is among the metal casting processes frequently employed when comparing casting and forging, especially in terms of surface finish.

Sand casting       

Sand casting involves creating a mold from a sand mixture and pouring molten metal into the cavity. Once the metal cools and solidifies, the sand mold is broken away to reveal the cast part. This technique typically produces larger, less complicated components.

Die casting

Die casting involves forcing molten metal under high pressure into a steel mold called a die. The metal solidifies quickly, and the die is opened to eject the finished part. This process, often compared to forging in discussions of casting vs forging, is ideal for materials like aluminum and magnesium and is particularly well-suited for mass production.

Shell mold casting

Shell mold casting is a variation of sand casting where the mold is a thin shell made from a sand-resin mixture. The sand is coated with a thermosetting resin and applied to a heated metal pattern, forming a hardened shell. It provides smoother surfaces than traditional sand casting, and it offers tighter tolerances.

sand casting

Understanding Forging

What is forging?

Forging is another useful manufacturing process that can be dated back to 4000-7000 BC; it involves shaping metal using compressive forces. Unlike casting, where metal is melted and poured into a mold, forging transforms solid metal into desired shapes through deformation. This fundamental difference between casting and forging results in distinct material properties. Forging enhances the metal’s mechanical properties, making forged components stronger and more reliable for critical applications.

At its core, forging is the process of forming metal by applying localized compressive forces. This is typically done by hammering, pressing, or rolling the metal at various temperatures. The key characteristic of forging is that it alters the metal’s internal structure, aligning the grain flow according to the shape of the part, which improves strength and durability—a characteristic that distinguishes it from casting in the broader context of casting and forging.

forging

Types of Forging Method

Open die forging

Also known as smith forging, open-die forging involves deforming the metal between multiple dies that do not enclose the metal entirely. The metal is compressed and manipulated freely to achieve the desired shape. This method is particularly suitable for large parts and custom shapes and it has lower tooling costs compared to closed-die forging.

Closed die forging

In closed-die forging, the metal is placed in a die resembling a mold, which is attached to an anvil. A hammer die is then dropped onto the metal, causing it to flow and fill the die cavities. In comparison to open die forging, this technique produces components with complex shapes and high accuracy. It is also very consistent in high-volume runs.

Cold forging

Cold forging is performed at or near room temperature. The metal is shaped through high-pressure compression without the need for heating. Usually, parts produced with cold forging have smoother surface and higher precision.

Hot forging

Hot forging involves heating the metal above its recrystallization temperature. This reduces the strength and increases the ductility of the metal, making it easier to shape. The main benefits of this method include preventing brittleness in parts, and it’s also great for producing more complex designs.

Roll Forging

Roll forging reduces the cross-sectional area of a metal bar by passing it through a pair of rollers with grooves shaped to form the desired profile. This process is very suitable for high-volume production, and it also greatly enhances mechanical properties along the length of the part.

Casting vs Forging Comparison

As mentioned at the beginning of this article, casting and forging are two fundamental manufacturing processes used to shape metal into desired forms. Although both methods produce metal components, they differ significantly in their techniques, the properties of the finished products, and their suitable applications. Let’s dive deep to look at how casting vs forging compare.

hot forging

Material Structure and Mechanical Properties

In casting, the molten metal solidifies within the mold, which can lead to a non-uniform grain structure due to varying cooling rates. This process may introduce internal defects such as porosity (small holes caused by trapped gases) and shrinkage cavities (voids formed as the metal contracts while cooling). These imperfections can make cast parts generally weaker and more brittle compared to forged parts.

aluminum casting
Die cast aluminum component

Forging, on the other hand, deforms and realigns the metal grains to follow the shape of the part, resulting in a continuous grain flow. This refined grain structure enhances the strength, toughness, and fatigue resistance of the forged component. Forged parts typically have fewer internal voids, leading to more reliable performance under stress. This difference in microstructure is a key factor in the casting vs forging debate.

An example of this is the crankshaft. Crankshafts in engines can be either cast or forged. Cast crankshafts are cheaper but less durable, making them suitable for standard engines. Forged crankshafts are stronger and more robust, used in high-performance or heavy-duty engines where durability is important. This comparison highlights the distinct characteristics of casting and forging.

Design Complexity and Precision

Casting excels at creating complex shapes with intricate details, including internal cavities and thin walls. The molten metal can fill intricate mold designs, allowing for components that might be impossible to produce through forging. However, the dimensional accuracy of cast parts may vary, and they often require additional machining to achieve precise dimensions and tolerances.

Forging is better suited for simpler shapes that require high strength. While closed-die forging allows for some complexity, it is generally less suitable for very intricate designs or parts with internal cavities. The increased complexity can also lead to higher tooling costs in forging due to the need for custom dies. This is a crucial consideration when deciding between casting and forging.

forged aluminum component

To give you a perspective, in a car, engine blocks are typically cast because they require complex internal passages for coolant and lubrication. In contrast, connecting rods, which need high strength and have a simpler shape, are commonly forged.

Size and Weight of Components

Casting is capable of producing components ranging from very small parts to extremely large ones, such as ship propellers and heavy machinery components. The weight of cast parts can vary widely, this makes casting a versatile option for different sizes.

stainless steel casting

Forging is generally limited to smaller or medium-sized parts due to equipment constraints and the immense forces required for larger pieces. While open-die forging can produce larger parts than closed-die forging, these tend to have simpler shapes and require significant equipment investment. This size limitation is a key differentiator between casting and forging. In this regard, we can look at the production of large valves and pump housings; these are often cast due to their size and complexity, highlighting the advantages of casting for larger components. Conversely, bolts and gears, which are smaller and require high strength, are commonly forged, demonstrating the benefits of casting and forging for different size and strength requirements.

Surface Finish and Aesthetics

Castings may have a rougher surface finish when compared to forging because of the texture of the mold materials and the casting process itself. As a result, cast parts often require additional finishing processes such as machining, sanding, or polishing to achieve the desired surface quality. While considering surface roughness in casting vs forging, it’s important to note that some casting processes, like investment casting, can also produce very smooth surface finishes.

Forged parts generally have smoother surfaces, especially when produced through cold forging. The forging process compresses the metal’s surface, resulting in a cleaner finish that may require less finishing work.

Decorative items with ornate designs are often cast, despite the need for extra finishing, because casting can capture fine details. Hand tools like wrenches and hammers are forged, resulting in smooth surfaces and durable products ready for use with minimal finishing.

Though casting methods like investment casting and die casting can often produce smoother surface in comparison to processes like sand casting and shell molding, especially when you apply certain surface finishes such as polishing, spray-painting and machining.

investment casting shell making

Production Volume and Cost

When comparing production volume and cost between casting and forging, the first important thing to consider is tooling cost. Casting usually involves lower initial tooling costs, especially in methods like sand casting, where molds can be made quickly and inexpensively. This makes casting economical for both small and large production runs. The per-part cost can be lower due to less material waste and the ability to produce near-net shapes that require minimal machining.

Forging has higher initial costs because of the expensive dies and equipment required. However, forging becomes more cost-effective for large production volumes, as the high tooling expenses are spread over many parts. The per-part cost decreases with volume, making forging suitable for mass production where high strength is essential.

However, please note that these are just typical comparison between casting vs forging as a whole, we still need to look at each individual project because every single project or component is different, sizes, materials all matter in this case.

In some cases, prototype parts are often cast to reduce initial costs and allow for design adjustments. Mass-produced automotive components like gears and shafts are forged when high strength and uniformity are required, justifying the investment in tooling.

Material Utilization and Waste

Material utilization and waste are also valid concerns when comparing casting and forging. Casting tends to have less material waste because the metal is poured directly into the desired shape, and any excess metal (like sprues and runners) can be remelted and reused. This enhances material efficiency and reduces waste.

stainless steel casting wax mold

Forging may produce more waste due to the trimming of excess material and the need for machining to achieve final dimensions. While the scrap material from forging can be recycled, it requires additional processing, which can add to the overall cost and environmental impact.

Suitability for Different Metals

When comparing casting and forging for suitability with different materials, it’s important to note that both processes have unique material applications, as results can vary significantly even with the same metal. Casting is suitable for a wide range of metals and alloys, including those with low ductility that are difficult to deform, such as cast iron and certain aluminum alloys. This versatility allows casting to be used for various applications requiring different material properties.

Forging requires metals that have sufficient ductility to withstand deformation without cracking. Metals commonly forged include steel, aluminum, copper, and titanium alloys. These materials can be shaped under compressive forces without compromising their structural integrity.

casting and forging components

Comparison Table

To make things more intuitive, we listed a comparison table of casting and forging for your reference.

AspectCastingForging
ProcessMelting metal and pouring into molds to solidify.Shaping metal using compressive forces without melting.
Material StructureNon-uniform grain structure; potential internal defects like porosity and shrinkage cavities.Refined grain structure with continuous grain flow, enhancing strength.
Mechanical PropertiesGenerally lower strength; more brittle due to potential internal flaws.Higher strength, toughness, and fatigue resistance.
Design ComplexityExcellent for complex shapes and intricate details, including internal cavities.Better for simpler shapes; closed-die forging allows for some complexity.
Size CapabilitiesCan produce very large to very small parts.Typically limited to small to medium-sized parts; open-die forging can handle larger simple shapes.
Surface FinishMay have rough surfaces; additional finishing often required.Generally smoother surfaces; less finishing needed, especially in cold forging.
Tooling and Setup CostsLower initial costs; economical for various production volumes.Higher initial costs; more economical for large production volumes.
Material WasteLess waste; excess metal can be remelted and reused.More waste due to trimming; scrap can be recycled with additional processing.
Material VersatilitySuitable for a wide range of metals, including low-ductility alloys.Requires ductile metals that can withstand deformation without cracking.
Typical ApplicationsEngine blocks, pump housings, artistic sculptures, large machinery parts.Crankshafts, gears, bolts, high-strength components in automotive and aerospace industries.
Production SpeedFaster setup and production for small runs; molds can be quickly prepared.Longer setup time due to die preparation; faster production rates once set up for mass production.
Precision and TolerancesMay require machining for precise dimensions; tolerances are wider.Achieves closer tolerances; may require less machining.
Energy ConsumptionLower energy per part; melting is energy-intensive but efficient for large batches.Higher energy per part due to the forces required; heating in hot forging adds to consumption.
Environmental ImpactEmissions from melting metal; sand molds can create waste, though sand can often be reused.Noise and vibration from forging; energy consumption impacts; scrap can be recycled.

Choosing Between Casting and Forging

When to Choose Casting

Casting is ideal when the component has intricate designs, internal passages, or requires a high level of detail. It is suitable for very large parts that are impractical to forge and when using metals or alloys that are difficult to forge due to low ductility. Lower initial tooling costs make casting economical for small production runs or prototypes. In the context of casting and forging, casting offers advantages in complexity and cost-effectiveness for certain applications. This is a key difference between casting and forging.

When to Choose Casting

Casting is ideal when the component has intricate designs, internal passages, or requires a high level of detail. It is suitable for very large parts that are impractical to forge and when using metals or alloys that are difficult to forge due to low ductility. Lower initial tooling costs make casting economical for small production runs or prototypes.

castings

Final Thoughts

Understanding the differences between casting and forging helps in selecting the appropriate manufacturing process based on the specific requirements of the component, such as mechanical properties, design complexity, size, and cost. By carefully evaluating these factors, manufacturers can optimize production efficiency, product performance, and overall project success.

Selecting the right casting and forging manufacturers

Choosing the right manufacturing partner is crucial for successful metal component projects. Key factors include material expertise, production capabilities, quality control, and in-house resources.

Casting Expertise with Taiyuan Simis Investment Casting Co., Ltd.

Taiyuan Simis Investment Casting Co., Ltd offers comprehensive casting solutions, specializing in investment casting for intricate designs, sand casting for cost-effective large components, shell mold casting for improved surface finish, and die casting for high-volume production of precise parts (especially in aluminum and magnesium). Our in-house capabilities include tool making for rapid prototyping, machining for precise dimensions, heat treatment for enhanced mechanical properties, and surface treatments for improved performance and aesthetics.

casting and forging differences

Forging Expertise with Shanxi KSN Forging

Our forging branch, Shanxi KSN Forging, provides advanced forging services using state-of-the-art equipment, including hydraulic presses, forging hammers, ring rolling mills, and heat treatment furnaces. Shanxi KSN Forging specializes in producing high-strength, durable forged components for demanding applications.

Choosing the Right Process and Partner

Understanding the differences between casting and forging is essential. Casting is often preferred for complex shapes and large parts, while forging excels in producing high-strength components with simpler geometries.

Choose Taiyuan Simis and Shanxi KSN for Your Casting and Forging Needs

Taiyuan Simis Investment Casting Co., Ltd. offers comprehensive highly custom casting services and Shanxi KSN Forging offer comprehensive forging solutions. We are committed to providing high-quality parts that meet your exact specifications. Contact us today to discuss your project and discover how our expertise in casting and forging can benefit your business.

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