Two Arts of Reshaping Metal: Analysis of the Essential Differences Between Casting and Forging

In the spectrum of human industrial civilization, casting and forging are like two masters with distinct skills, jointly laying the foundation of modern manufacturing. Although both are dedicated to giving metals new forms and lives, their philosophical concepts, implementation paths, and ultimate outcomes are fundamentally different. Understanding the differences between them is not only a technical cognition but also a key to insight into materials science and engineering aesthetics.

I. Core Principles: The Fundamental Opposition between Liquid Forming and Solid Shaping

The most essential difference lies in the physical state of the metal during the processing.

The core of casting is “liquid forming”. It is similar to making ice cubes with water – first, the metal is heated to a completely liquid state, and then it is poured into a pre-made cavity (mold). After cooling and solidifying, a product with the same shape as the mold cavity is obtained. Its essence lies in “determining by the mold”, with extremely high freedom in form.

The core of forging is “solid shaping”. It is like a traditional blacksmith forging iron. The metal material (usually called the billet) remains solid throughout the processing. By applying huge pressure or impact force, it undergoes plastic deformation in the solid state to obtain the desired shape and improved internal structure. Its essence lies in “changing by force”, emphasizing the alteration of shape and the optimization of structure.

This fundamental difference in physical state directly leads to a series of differences in subsequent performance and characteristics.

II. Structure and Performance:

The different processing methods profoundly change the micro-world inside the metal, thereby determining the mechanical properties of the parts.

2.1 Casting structure: Liquid metal gradually cools and crystallizes in the mold, forming casting structures such as dendrites. Although it can be optimized through advanced processes (such as precision casting), there are inevitably some inherent defects inside, such as shrinkage cavities, shrinkage porosity, gas holes, and composition segregation. This results in relatively lower toughness and impact performance of castings, making them more prone to fracture from these weak points when subjected to strong impact or fatigue loads.

2.2 Forging structure: The magic of forging lies in its ability to “turn the rotten into the miraculous”. The huge pressure can weld the internal holes and defects of the raw material, break up the coarse casting dendrites and carbides, and refine the grains through the recrystallization process. More importantly, forging can streamline the metal’s fiber structure according to the shape of the part, making the grain flow consistent with the part’s shape and forming continuous “streamlines”. This is like a skilled craftsman smoothing and strengthening the chaotic wood grain into a smooth and tough texture. The result is that forgings usually have much higher strength, toughness, fatigue strength, and reliability under impact and vibration loads than castings.

III. Process and Design:

3.1Design and shape complexity:

Casting has an unparalleled advantage in shape freedom. Almost any complex internal and external structure you can imagine (such as complex cavities, waterways, blades, etc.) can be achieved in one pour, making it very suitable for manufacturing parts with complex structures, especially those with complex internal cavities, such as engine blocks, machine tool beds, and art sculptures.

Forging, due to being a solid deformation, is difficult to form complex internal cavities and three-dimensional curved structures. The shapes of forgings are usually relatively simple, mostly solid parts such as shafts, discs, and blocks. Its advantage lies in performance rather than the intricacy of form.

3.2 Materials and costs:

Casting is applicable to almost all metal materials, especially those with high brittleness and difficult to process under pressure (such as cast iron). The mold cost is high, but the single-piece production cost is relatively low, making it particularly suitable for mass production.

Forging is mainly used for materials with good plasticity, such as carbon steel, aluminum alloys, and titanium alloys. It requires huge forging equipment, has high energy consumption, and the material utilization rate is often lower than that of casting (as excess parts need to be milled off), thus the production cost is usually higher.

Four. Application scenarios:

Choosing between casting and forging is never a matter of superiority or inferiority, but rather a precise match based on design requirements.

When you prioritize “complexity of shape” and “economic efficiency of production”, casting is the preferred choice.

Typical products: automotive engine blocks, transmission cases, water pump impellers, fire door hardware, exquisite bronze statues.

When you prioritize “ultimate strength, reliability and safety”, forging is the only option.

Typical products: engine crankshafts and connecting rods; turbine discs and landing gears in aerospace; gears and spindles in heavy machinery; wrenches and hammer heads in tools; and high-quality kitchen knives in our daily lives.

Supplier

Luoyang Fonyo Heavy Industries Co., Ltd, founded in 1998,is a manufacturer in railway casting parts. Our factory covers an area of 72,600㎡, with more than 300 employees, 32 technicians, including 5 senior engineers, 11 assistant engineers, and 16 technicians. Our production capacity is 30,000 tons per year. Currently, we mainly produce casting, machining, and assembly for locomotive, railcar, high-speed trains, mining equipment, wind power, etc.
We are the railway parts supply to CRRC(including more than 20 branch companies and subsidiaries of CRRC),Gemac Engineering Machinery,Sanygroup, Citic Heavy Industries,etc. Our products have been exported to Russia, the United States, Germany, Argentina, Japan, France, South Africa,Italy and other countries all over the world.
Contact Information:
Email:sales@railwaypart.com
Mobile:008615515321683