Also known as Lost Wax Casting, Investment Casting is a process that has a rich history with its roost well centred in 5 000 B.C. Very well established in history, particularly in China, this casting process still continues to develop for new applications in a wide variety of materials for an ever wider market application.
|Page 1: History|
|Page 2: Types of Products Made|
|Page 3: Casting in China|
|Page 4: The Pros and Cons|
|Page 5: Latest Developments|
|Page 6: ChinaSavvy Videos|
Traced back to 5 000 B.C., this process was typically used in China to cast materials, such as bronze, in order to make personal ornaments. It can also be traced through 3 200 B.C. where instances of this casting process was found in Israel and Mesopotamia. It spread around the Mediterranean, through Asia to South America and to Africa.
Around 1 100 A.D. the process becomes well documented when Theophilus Presbyter wrote a paper about the process – some of which was content gathered from other sources. It is believed that this paper by Presbyter led to the adoption of this process, particularly for non-ferrous metals (metals that do not contain iron) by Benvenuto Cellini, whose investment cast bronze statue (Perseus with the Head of Medusa) still stands in the Loggia dei Lanz in Italy.
The process continued to be used for pieces of jewellery and art simply because of its relatively simple pattern making process, cheap price and flexibility. Artisans of that time were also able to flex and shape pieces easily.
In the 20th Century a wider and mass market use of the investment casting process started. In 1907 Dr. William H. Taggart published a paper in which he describes the use of a lost wax process he used in order to make teeth and dental plates.
Driven by World War II, another big development within this process takes place. The need for a faster production rate, especially when it came to ammunitions and aircraft, was needed. Products produced were often that of complex and hollow shapes. Combined with the scarcity of some materials used for patterns, the diversification of the materials used in the process took a big leap forward.
The lost wax casting process was further developed to allow the casting of ferrous alloys (alloys that have iron as its main constituent) and other materials that are difficult to undergo machining, such as titanium.
Being able to produce near net shape products that require less secondary machining, while producing less waste, was greatly beneficial.
Starting at small and decorative items made of non-ferrous metals, today we see it used in the production of large, industrial components using both non-ferrous and ferrous materials. Some the items produced using lost wax casting include entire aircraft doors made of aluminium and even steel castings that weight up to 300 kilograms.
In China, the casting process has evolved with variants to suit the three main key market areas, which can be described as:
- Mid temperature wax (also known as green wax) Silicon Sol process
Used with a wide range of both ferrous and non-ferrous materials, this process produce castings that have a high tolerance and a better surface finish.
- Low temperature wax (also known as white wax) and Silicon Sol process
This process can only be used on carbon steels and a limited range of steel alloys. This process does produce a better surface tolerance and surface finish than the Low temperature wax (also known as white wax) sodium silicate process.
- Low temperature wax (also known as white wax) sodium silicate process
This variant of the casting process is only used for carbon steels and a limited range of steel alloys.
Still developing, this casting process is both an effective and popular process used in China and the rest of the world.
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