Comparative Analysis of Casting and Forging

 

What is the difference between casting and forging? How to choose? Do you know all of this?

In the modern manufacturing industry, casting and forging are two common metal forming processes, which show unique advantages in different application scenarios. Although both belong to the field of metal forming, the process principles, production processes and scope of application of the two are very different. This article, as a selection guide, will take you to a deep understanding of the differences between casting and forging, and help you choose the processing method that best suits your project needs.

1. Introduction to Casting Process

Casting is the process of pouring metal into a mold after melting it, and then cooling and solidifying it. This process is particularly suitable for manufacturing parts with complex shapes and variable structures, and can meet the production needs of multiple varieties, small batches and even large-sized products.

There are various types of casting processes, and the common ones include:

● Die casting: The molten metal is injected into a precision mold at high pressure and high speed. It is often used for light alloy parts with large-volume demand, stable casting dimensions and high precision, such as automobile gearbox housings, electronic device housings, etc.

● Low-pressure casting: Pressing liquid metal into the mold at low pressure, compared with die casting, is suitable for parts with high airtightness requirements. The finished product has dense structure and few internal defects, which is suitable for medium-volume production.

● Gravity casting: Relying on the natural filling of the metal's own weight, it is suitable for the production of parts with medium complexity. The mold structure is relatively simple and the cost is low.

● Investment casting (lost wax casting): After the shell is formed by the wax mold, the metal is poured. It is suitable for manufacturing small parts with complex details and high surface quality requirements. It is the one with the highest manufacturing precision among the four processes mentioned above.

Advantages of casting

Casting has many advantages, such as choosing different metal materials and different casting processes, and can flexibly produce lightweight parts, extremely heavy parts, small parts and large parts. It can be said that in terms of the weight and size of the parts, the casting process can meet all your needs.

Casting has a wide range of applicable materials and flexible raw material processing. Special alloy elements (such as chromium, molybdenum, nickel, etc.) can be flexibly added during the smelting stage to improve the performance of the material and meet the application requirements.

For medium and large batches, the more parts produced, the lower the cost of the mold, and the longer the service life of the metal mold, which can be used repeatedly.

In addition, for parts with complex structures that are difficult to machine, casting shows irreplaceable forming capabilities in this case.

2. Overview of forging process

Unlike casting, forging is a processing method that applies external force to the metal in a solid state to shape it. The metal billet is extruded by a die hammer, press or other special equipment to flow along the shape of the mold in a hot or cold state to form the required geometric structure.

Common classifications of forging include:

● Cold forging: Processing metal at room temperature, suitable for high-precision forming of small-sized parts.

● Warm forging: Heating the metal to below the recrystallization temperature, taking into account both processing performance and finished product strength.

● Hot forging: Heating the metal to above the recrystallization temperature for forming can significantly improve the plasticity and structure of the metal, and is widely used in the production of medium and large, high-strength components.

Advantages of forging

During the forging process, the internal grain structure of the metal will rearrange with deformation. In short, this change will make the forging have extremely high strength, toughness and impact resistance.

In addition, forging can effectively reduce internal defects such as pores and inclusions, and improve the overall density and structural reliability.

The characteristics of forging also include short processing cycle, suitable for medium- and long-term stable mass production, and high degree of equipment automation. However, correspondingly, the mold cost is high, and there are certain restrictions on the geometry of the parts. It is not suitable for designs with large wall thickness changes or extremely complex structures.

3. The key difference between casting and forging

The performance differences and application differences between casting and forging in actual applications are mainly reflected in the following aspects:

(1) Part size and weight

Casting is almost not limited by size. It can produce light, heavy, small and large parts as long as the right materials and processes are selected; while forging is affected by equipment capacity and material plasticity. It is only suitable for the production of medium-sized parts, and it cannot be too complex.

(2) Structural complexity

Casting can easily cope with designs with complex cavities and precise details; while forging is more suitable for parts with simple contours and high strength requirements, such as shafts and connecting rods. In this respect, casting is superior to forging.

(3) Flexibility of materials and alloys

Foundries can flexibly add special alloys during the smelting stage according to specific performance requirements, while the billets used for forging usually come from steel mills, and the types of materials available are limited.

(4) Strength and durability

Forgings have higher mechanical strength and impact resistance due to their dense grain structure, which is also the biggest advantage of forging; castings have more advantages in wall thickness and uniformity, and both thick-walled parts and thin-walled parts can be completed by casting.

(5) Cost factors

The cost of casting and forging cannot be compared in a single way. The price of castings and forgings depends on many variables. The cost may be lower in one case and higher in another. Specific factors that affect the price of parts include the following:

Production batch

Metal material price

Shape complexity

Specific process of casting or forging

Post-processing cost

Detection cost

4. Choose the right processing method for your parts

Before deciding whether to use casting or forging, it is recommended to evaluate from the following perspectives:

Does the part have a complex geometry or internal cavity?

Does the project budget support the mold development cost?

Does the part require high strength or high impact resistance?

Is the material a general alloy, or does it require customized proportions?

How long is the annual output and life cycle of the project expected to be?

Generally, if the goal is high-strength, impact-resistant shafts or load-bearing parts, forging is preferred; if it is for complex structures, large sizes or high alloy customization, casting will be more suitable.

5. Can casting and forging processes be used in combination?

Yes, in actual engineering, the combination of casting and forging is a common and effective manufacturing strategy, especially for complex parts that require both performance and shape.

A common combination is "casting forming + forging/machining". For example, precision casting is first used to obtain a blank that is close to the final shape, and then forging or machining is used to further optimize the organizational performance and dimensional accuracy at the key stress-bearing parts. We at Xavier use this method to produce parts, which can not only reduce the waste of raw materials, but also retain the complex shape, while strengthening the mechanical properties of important areas.

Another way is to manufacture different parts by casting and forging, and finally combine them into a component by welding, bolting or shrink fitting. For example, casting a hollow shell, forging a high-strength flange, and then assembling them into one, taking into account both lightweight and load-bearing capacity.

6. Conclusion

Whether it is casting or forging, they have various application fields. Understanding their process characteristics and application boundaries will help you make wise manufacturing choices for each engineering project.

With many years of experience in casting and precision machining, Xavier can provide you with a one-stop solution covering material selection, structural optimization, and process matching to help produce high-quality and efficient metal parts. If you are in the project evaluation or product development stage, please feel free to contact us for technical consultation and support.