Casting is a metalworking process that has been practiced by humans for thousands of years, with a history spanning approximately 6,000 years. In ancient China, between 1700 and 1000 BC, the bronze casting industry reached its peak, showcasing advanced techniques and craftsmanship. Notable examples include the massive 875 kg bronze vessel from the Shang Dynasty, the Zeng Houyi bell set from the Warring States period, and the translucent mirrors from the Western Han Dynasty. Most early castings were used for tools, agricultural implements, religious rituals, and daily life, often exhibiting strong artistic value. At the time, casting developed alongside ceramic production and was significantly influenced by pottery techniques.
In 513 BC, China became the first to cast iron, producing a piece weighing around 270 kilograms. Europe began producing cast iron parts roughly in the 8th century. The introduction of cast iron expanded the range of applications for castings. For example, in the 15th and 17th centuries, Germany and France installed cast iron water pipes to supply drinking water to cities. After the 18th-century Industrial Revolution, industries like steam engines, textile machines, and railways emerged, leading to a new era for casting technology as it supported large-scale industrial development.
Throughout the 20th century, casting technology advanced rapidly. One key driver was the evolution of product design, which demanded better mechanical and physical properties from castings while maintaining good machinability. Additionally, the growth of industries such as machinery, chemicals, and instrumentation provided favorable material conditions for foundries. Developments in testing methods improved casting quality control, and innovations like electron microscopy allowed deeper exploration of metal crystallization, advancing the theoretical understanding of solidification and guiding practical casting processes.
During this period, many new high-performance casting alloys were introduced, including ductile iron, weldable malleable cast iron, ultra-low carbon stainless steel, and various aluminum, titanium, and nickel-based alloys. New techniques such as inoculation treatment for gray cast iron also enhanced casting adaptability.
After the 1950s, new technologies like wet sand high-pressure molding, chemical hardening sand, and vacuum molding significantly improved the dimensional accuracy, surface finish, and overall quality of castings. Foundry working conditions and environmental hygiene also saw major improvements. Among the key advancements, the gestation treatment of gray cast iron and chemical hardening sand molding played a crucial role in breaking traditional methods and opening new possibilities for the casting industry.
Casting is typically classified based on the molding method, commonly divided into sand casting and special casting. Sand casting includes wet sand, dry sand, and chemically hardened sand types. Special casting uses different materials, such as investment casting, shell molding, and metal casting, including centrifugal and pressure casting.
The casting process involves three main stages: metal preparation, mold making, and casting processing. Cast metals are usually alloys made from base metals and other elements, known as cast alloys—such as cast iron, cast steel, and non-ferrous alloys. Metal melting is not just a simple process; it involves precise control of temperature, composition, and purity to meet casting requirements. Additional treatments like desulfurization or vacuum degassing may be applied to improve quality.
Mold preparation varies depending on the casting method. In sand casting, it involves preparing molding materials and creating cores. Equipment like sand mixers and core shooting machines help produce accurate molds. Once the casting is removed from the mold, it requires cleaning to remove gates, risers, and excess sand. Cleaning processes include shot blasting and gate cutting, which can be labor-intensive and require careful consideration during mold design.
Casting is an economical way to produce complex-shaped parts, especially for components like engine blocks, ship propellers, and intricate art pieces. Some difficult-to-machine materials, such as nickel-based alloys in gas turbines, can only be formed through casting. Castings come in a wide range of sizes and weights, using almost any type of metal, and offer diverse properties like wear resistance and corrosion resistance, which other forming methods cannot match.
However, casting has unique challenges, including environmental pollution from dust, gases, and noise. Compared to other manufacturing processes, it poses greater environmental risks and requires effective control measures.
Modern casting trends focus on higher performance, precision, and surface quality, along with energy efficiency and environmental sustainability. This drives the development of new alloys, smelting techniques, and eco-friendly equipment. As automation increases, flexible production systems will become more important to accommodate varied product demands.
Foundry workers continue to study metal solidification and sand compaction using advanced electronics and testing methods. The integration of robotics and computer systems in foundry operations is also expanding, enhancing both production efficiency and management capabilities.
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