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Casting

2019-10-31

Casting is the manufacturing way to form metal parts by using all kinds of casting processes. In casting, meIted metal will be pouring or injected into the prepared mold. Then solidified into solid metal shape while cooling under room temperature, finally sand or shot blasted to net shape product.

History of Casting

The melting ovens of the early Iron Age can partly be traced back to ceramic burning ovens. The model and mould building was mastered very well from the beginning. Lost moulds made of loam and clay, wax models, single piece-work as well as permanent moulds made of stone and metal for the serial production of casting parts were already used. The production of hollow spaces by using cores, has already been proved by the oldest casting parts discovered.

After the great performances in the field of casting during antiquity, it took a long time to match the former level in the occidental Middle Ages. However, whereas there is hardly any continuous documentation about casting technology during the antiquity, the German monk Thophilus already examined the forming and casting very intensively around 1140. The “fireworks books”–especially the book by Italian Biringuccio – were written after 1500 AD should also be mentioned in this context. Loam, plaster and wax were the most important working materials. Crucible and later flame ovens were available for the melting of copper, tin and lead alloys. Casting by means of forming sand was common for small parts; permanent moulds were of great importance for the serial casting of lead and tin materials. In the beginning, the casting of bells and other clerical equipment was the main focus. Relief casting matched the artistic quality of the antique casting at the beginning of modern times.

The China casting had mastered the melting of iron since 500 BC, 2.000 years before the Europeans. New excavations proved that they succeeded in the mass production of cast tools and farm equipment after the development of iron casting.

From the early beginning to present day, casting has been used to create lots of metal components for all industries.

Types of Casting

Modern casting has become a cost-effective metalworking method to produce metal components in cast steel, cast iron and cast aluminum, ect. Here, we would like to introduce the common casting methods according to different cast metals.

Types of Casting for Steel

Investment Casting, also know as precision casting, type of casting using an expendable pattern of wax, which is “invested” or surrounded by a molding medium in slurry or liquid form. After the molding medium has solidified, the pattern is removed by subjecting the mold to heat, leaving a cavity for reception of molten metal.

Water glass casting is the investment casting process to produce small and medium type carbon and alloy steel castings with smooth surface and tight tolerances. It is the cheapest casting method to produce precision steel castings.

Silica sol casting is the other investment casting process which is open to all types of precision steel castings, but more widely used to produce stainless steel castings. Compared with water glass investment casting, the cost is much higher, but better surface finish and dimension accuracy.

In conclusion, for steel castings weighting less than 60kg, investment casting is the right solution.

For large steel castings, sand casting is used.

Types of Casting for Iron

There are also two types of casting processes to produce iron castings. Well known casting type to produce iron castings is sand casting.

Sand casting, also known as sand molded casting, is the casting process that uses sand as the mold material. Molds made of sand are relatively cheap, and sufficiently refractory even for steel foundry use. In addition to the sand, a suitable bonding agent (usually clay) is mixed or occurs with the sand. The mold cavities and gate system are created by compacting the sand around models called patterns, by carving directly into the sand.

Sand casting is available to produce all types of iron castings. More often made iron castings by sand castings are grey iron castings and ductile iron castings.

Types of Casting for Aluminum

Aluminum is one of the popular metals to be applied in different industies for its light weight. Even if casting, there also contains several types: High pressure die casting and gravity casting.

High temperature die casting is the casting method that produce aluminum and zinc alloys by injecting liquid metals into molds under high temperature. Common aluminum alloys produced in die casting method are: A356, A380 and ADC-12. Due to the high cost of die casting molds, it is more cost effective for large production runs. Die casting is the ideal casting process for aluminum castings in thin wall thickness.

Gravity casting is another casting type to make thick aluminum castings. Compared with aluminum die casting method, the surface will be rougher, but lower cost. And machining is usually operated when there is a high requirement on dimensional accuracy and surface roughness.

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